Vetiver grass or Chrysopogon zizanioides (L.) Roberty (1960) is a sterile grass which can regenerate vegetatively from clumps of the rootstock. This, as well as its vigorous and deep root system and flood tolerance makes it an ideal candidate for the use in soil remediation and erosion control. In South Africa, Hydromulch (Pty) Ltd. is part of the landscape, soil reclamation and erosion control industry. The company uses vetiver grass on a wide scale and has accumulated a collection of isolates to serve as possible germ lines for industrial use. Due to the different approaches in environmental management as well as environmental factors, a variety of ecotypes form during the planting and acclimatisation of this genus. Chrysopogon nigritanus (Benth.) Veldkamp (1999), which is a native species to Africa, is closely related to C. zizanioides and differs only slightly from C. zizanioides on a morphological level. The major difference between the two species is that C. nigritanus is able to seed freely and thus the use of this species should be avoided. The need arose to screen other non-fertile plants to uncover additional genotypic variety to enable diversification of vetiver plantings. The aim of this study was to characterise the genotype of 19 isolates of vetiver obtained from Hydromulch (Pty) Ltd. via sequencing analyses of three DNA fragments, ITS, ndhF and rbcL. In addition, the radial root anatomy was also investigated and compared with the genetic analyses. According to the results generated during this study, very little or no genotypical differences exist amongst the different isolates available from the Hydromulch (Pty) Ltd. plant collection. Only in the case of the ITS inference were differences observed between three of the studied isolates. There was no significant difference between the different isolates based on the root anatomy, with the exception of two of the studied isolates which formed starch granules. / MSc (Botany), North-West University, Potchefstroom Campus, 2014

Vetiver grass or Chrysopogon zizanioides (L.) Roberty (1960) is a sterile grass which can regenerate vegetatively from clumps of the rootstock. This, as well as its vigorous and deep root system and flood tolerance makes it an ideal candidate for the use in soil remediation and erosion control. In South Africa, Hydromulch (Pty) Ltd. is part of the landscape, soil reclamation and erosion control industry. The company uses vetiver grass on a wide scale and has accumulated a collection of isolates to serve as possible germ lines for industrial use. Due to the different approaches in environmental management as well as environmental factors, a variety of ecotypes form during the planting and acclimatisation of this genus. Chrysopogon nigritanus (Benth.) Veldkamp (1999), which is a native species to Africa, is closely related to C. zizanioides and differs only slightly from C. zizanioides on a morphological level. The major difference between the two species is that C. nigritanus is able to seed freely and thus the use of this species should be avoided. The need arose to screen other non-fertile plants to uncover additional genotypic variety to enable diversification of vetiver plantings. The aim of this study was to characterise the genotype of 19 isolates of vetiver obtained from Hydromulch (Pty) Ltd. via sequencing analyses of three DNA fragments, ITS, ndhF and rbcL. In addition, the radial root anatomy was also investigated and compared with the genetic analyses. According to the results generated during this study, very little or no genotypical differences exist amongst the different isolates available from the Hydromulch (Pty) Ltd. plant collection. Only in the case of the ITS inference were differences observed between three of the studied isolates. There was no significant difference between the different isolates based on the root anatomy, with the exception of two of the studied isolates which formed starch granules. / MSc (Botany), North-West University, Potchefstroom Campus, 2014

Human-induced land degradation and climate change can reduce agricultural productivity and increase susceptibility to food shortages at local and global scales. Planting perennial crop species, such as fruit and nut crops, may be an intervention strategy because of their beneficial contributions to sustainable agriculture and human nutrition. Many perennial temperate fruit and nut species are however, particularly vulnerable to frost events, drought, insufficient chill hours, and disease and insect outbreaks. Modifying these species to yield harvests under a wider range of biotic and abiotic conditions may increase the value and long-term viability of perennials in agroecosystems. This dissertation examines adaptation and ecogeography in temperate perennial fruit crops, using apple (Malus sensu lato) as an example for case studies. The resilience of feral domestic apple trees in abandoned farmstead orchards throughout the southwestern U.S. indicates plasticity in adapting to local environmental conditions. Dendrochronology reveals these trees tend to persist where they have access to supplemental water, either as shallow groundwater or irrigation. While domestic apples are cultivated under a range of growing conditions, wild relatives of agricultural crops may further expand the cultivable range of the species. Crop wild relatives are species closely related to agricultural species, including progenitors that may contribute beneficial traits to crops. Sampling the genetic variation in crop wild relatives may benefit from ecological genetics and GIS theory to reveal genetic structure. The Pacific crabapple is an example of a wild apple relative that may contain genetic variation useful in apple breeding. Species distribution modeling of the Pacific crabapple identifies a narrow climatic window of suitable habitat along the northern Pacific coast, and genetic fingerprinting reveals a highly admixed genetic structure with little evidence of natural or cultural selection. While the moist coastal Pacific Northwest is not necessarily characteristic of many apple-growing regions, the species may have useful adaptations transferable to domestic apples. Genetic resources offer a promising source of raw material for adapting crops to future agricultural environments; their characterization, conservation, and use may offer important contributions to adaptation and use of perennial crops in agro-ecosystems.

Polymorphism is the existence of multiple phenotypes within a given species in a population. In social insects, worker polymorphism plays a key role in maximizing the effectiveness of the division of labor. Some ants have an extreme form of worker polymorphism where workers have a broad size range and multiple size modes. Pheidole ants, for example, consist of both highly polymorphic species as well as those with relatively low polymorphism. Here, we examined why different Pheidole species have different degrees of polymorphism and how polymorphism is produced. We thoroughly characterized the worker caste systems of P. spadonia, P. rhea, P. obtusospinosa, and P. tepicana. There were significant differences among the four species in size range, number of size modes, caste ratios, allometry, and caste biomass allocation. An examination of worker caste traits of P. spadonia, P. rhea, and P. obtusospinosa revealed that as head size increased for all three species: (1) mandibles became broader and less serrated, (2) head muscle volume increased, and (3) bite force increased. These traits of large supersoldiers are likely adapted for crushing while those of small minors are likely for cutting. Foraging experiments showed that P. spadonia, P. rhea, and P. obtusospinosa used their workforce in different ways for food processing outside the nest. For P. rhea, the frequency of supersoldiers involved in food processing increased as the processing level required increased. However, P. obtusospinosa supersoldiers were rarely found processing food outside the nest and P. spadonia soldiers assisted in processing dead prey but did not help at all in processing live prey. P. obtusospinosa and P. spadonia workers may be more involved with other colony tasks. This hypothesis was confirmed when field observations of P. obtusospinosa showed supersoldiers participating in head-blocking at their entrance to fend off invading army ants; no other castes exhibited this behavior. Lastly, we tested genetic influences on worker polymorphism. We found that as colony genetic diversity increased (via polyandry), the degree of polymorphism increased. We also showed evidence of paternal genes influences on the development of worker castes in the highly polymorphic P. rhea.

Klimawandelmodelle sagen für Deutschland sowohl höhere Jahresdurchschnittstemperaturen als auch eine Abnahme von Niederschlägen in den Sommermonaten voraus. Mögliche Konsequenzen für Bäume sind eine verlängerte Vegetationsperiode, ein erhöhtes Spätfrostrisiko und mehr Trockenstress während des Sommers. Diese veränderten Umweltbedingungen könnten zu Veränderungen der Konkurrenzverhältnisse zwischen Baumarten führen. Die Rotbuche (Fagus sylvatica L.) ist eine der wichtigsten Laubbaumarten Mitteleuropas. Daher ist das genetische Anpassungspotential dieser Baumart an den Klimawandel von großem Interesse. In dieser Studie wurden sowohl die neutrale als auch die adaptive genetische Variation der Buche untersucht. Dafür wurde ein Translokationsexperiment mit Nachkommen von Buchenpopulationen, die unter verschiedenen Umweltbedingungen in Norddeutschland wachsen, etabliert. Wiederholte Aufnahmen wichtiger phänotypischer Merkmale (Höhe, Austrieb, Trockenstresssensitivität, Sterblichkeit) zeigten signifikante Unterschiede zwischen den Populationen. Interessanterweise zeigten Populationen mit einer größeren geographischen Distanz teilweise ähnlichere Phänotypen als benachbarte Populationen. Die neutrale genetische Variation der untersuchten Sämlingspopulationen wurde anhand neun verschiedener Mikrosatellitenmarker analysiert. Zwischen den analysierten Buchenpopulationen wurde nur eine geringe genetische Differenzierung ermittelt. Die genetische Diversität war hoch und statistisch nicht signifikant unterschiedlich von den Altbeständen, aus denen sie stammten. Die hohe genetische Diversität ist eine gute Basis für Adaption, allerdings könnte sie wahrscheinlich nur eine kurzfristige Anpassung an den Klimawandel ermöglichen. Daher ist es wichtig, Einblicke in die genetische Basis von klimawandelrelevanten Merkmalen zu gewinnen. Deshalb wurden in dieser Studie Kandidatengene für das Austriebsverhalten untersucht. Bei der Analyse von Fragmenten von zehn verschiedenen Kandidatengenen wurden 20 Indels und 116 SNPs identifiziert. Insgesamt wurden 46 SNPs erfolgreich zur Genotypisierung von über 1.400 Individuen, die aufgrund ihres Austriebsverhaltens ausgewählt wurden, verwendet. Assoziationsanalysen wurden durchgeführt, um potentiell adaptive SNP-Marker zu identifizieren. Diese ergaben unter einem „generalisierten linearen Modell“ 23 signifikant mit dem Austrieb assoziierte SNPs. Ein zusätzlich verwendetes „gemischtes lineares Modell“ ergab nahezu gleiche Ergebnisse. Die phänotypische Variation, die durch signifikant mit dem Austrieb assoziierte SNPs erklärt wird, war niedrig (R2 < 2,2), aber in Übereinstimmung mit anderen Studien mit Waldbaumarten. Zusätzlich zu den Assoziationsanalysen wurden auch FST-Outlier-Analysen durchgeführt. Diese ergaben sieben verschiedene SNPs, die potentiell unter ausgleichender oder gerichteter Selektion stehen. Insgesamt wurden vier potentiell adaptive SNPs gleichzeitig durch Assoziations- und Outlier-Analysen identifiziert. Diese könnten die höchste Wahrscheinlichkeit aufweisen, an der Ausprägung des Austriebsverhaltens beteiligt zu sein. Allerdings sind viele potentiell adaptive SNPs, die in dieser Studie identifiziert wurden, nicht-kodierend oder synonym und somit nicht die kausativen SNPs, sondern eher gelinkt mit ihnen. Allerdings wurde in dieser Studie ein geringes Kopplungsungleichgewicht (linkage disequilibrium) gefunden. Somit könnten die kausativen SNPs in naher Umgebung liegen. Die in dieser Studie identifizierten potentiell adaptiven SNPs sollten in weiteren Studien mit zusätzlichen Populationen bestätigt werden.

The genus Blastocystis has recently attracted the attention of scientists, especially parasitologists. Similarly to the related opalines and proteromonads, Blastocystis is anaerobic and lives endobiotically in the intestine of various animals. This organism is also often found in humans, where it is associated with irritable bowel syndrome, though its pathogenic potential remains uncertain. The genus Blastocystis is remarkable for its rich genetic diversity. The taxonomy of Blastocystis is inconsistent and problematic. The strains isolated from homoiothermic vertebrates are divided into 17 subtypes, while strains from poikilotherms are either classified as separate species or are not considered in taxonomic studies at all. The aim of the study was to further examine the genetic diversity of the genus Blastocystis. We determined SSU rDNA sequences of 38 strains isolated from poikilothermic vertebrates and arthropods. The results of our phylogenetic analysis showed that Blastocystis is considerably diverse in these hosts, and we defined 21 new subtypes. The total number of known subtypes of Blastocystis has thus increased to 38. We also examined light-microscopical morphology of some strains. Most of the newly defined subtypes show identical morphology, ST20 (Blastocystis geocheloni) is an exception,...

A eux seuls, le Nigeria, la République Démocratique du Congo, l'Ouganda, l'Ethiopie et la Tanzanie représentent 50% de la mortalité liée au paludisme et 47% du total des cas de paludisme. Cependant, la diminution du nombre de cas et l'augmentation des activités de lutte à l'échelle mondiale sont autant de bonnes nouvelles encourageantes qui font déclarer à l'OMS que le paludisme peut être contrôlé et plus tard éliminé. Les recommandations des experts de la lutte contre le paludisme à l'échelle mondiale recommandent de cibler les zones où l'élimination est possible, les zones de faible transmission, et de là progresser vers les zones plus impaludées. Cela impose une connaissance précise de la situation du paludisme dans la région concernée. Les ensembles géographiques régionaux où la transmission du paludisme connait une diminution sensible, comme la Corne d'Afrique, et ayant des frontières extrêmement poreuses aux mouvements de populations humaines donc aux pathogènes, sont donc à cibler en priorité. Cela nécessite une évaluation du niveau de transmission et du risque de résurgence potentiel, posé par l'importation de nouvelles souches, afin d'aboutir à une élimination durable. Dans ce contexte, la République de Djibouti, ayant montré une prévalence extrêmement faible au cours de ces dernières années, s'est lancée dans une tentative de pré-élimination du paludisme. L'objectif de notre étude a été d'observer l'évolution, sur une durée de onze années (1998-2009), du taux d'incidence de l'infection palustre, du niveau de transmission du paludisme, de la possibilité d'importation depuis les pays voisins et enfin, de la distribution des vecteurs de la maladie. / Nigeria, the Democratic Republic of Congo, Uganda, Ethiopia and Tanzania represent 50% of malaria deaths and 47% of total malaria cases. However, the decrease in the number of cases and worldwide increased control activities were encouraging news which lead the WHO to declare that malaria can be controlled and eliminated later. The recommendations of experts in the worldwide fight against malaria recommend targeting areas where elimination is possible, areas of low transmission, and hence moving towards areas more affected by malaria. This requires a precise knowledge of the malaria situation in the region. Geographical regional assemblies where malaria transmission is experiencing a significant decrease, as the Horn of Africa, and having extremely porous frontiers to the movement of human populations, therefore pathogens, must be the priority target. Thus an assessment of the level of transmission and the risk of potential recurrence, posed by the importation of new strains, was indispensable in order to achieve sustainable elimination. In this context, the Republic of Djibouti, who showed extremely low prevalence in recent years, is embarked on an attempt to pre-eliminate malaria. The aim of our study was to observe changes, over a period of 11 years (1998-2009), in the level of malaria occurrence, malaria transmission, but also the level of its potential importation from neighboring countries and finally the vectors population dynamics. These results could serve as a basis of reflection, for the health authorities of the country or international partners, to a possible adjustment of the current policy of fight against malaria.

Research Report for Masters degree Faculty of Health Sciences / Since the early 1980's, global trends in dental caries have indicated that 80% of the caries is present in approximately 20% of the population which suggests a variation in susceptibility to the disease. In Sub-Saharan Africa and in South Africa, caries prevalence has shown a downward trend in preschool and school children. The reasons for this decline are obscure and have not been attributed to dietary habit, oral hygiene, the use of fluoride dentrifices or to any public health prevention program. Furthermore, the numbers of mutans streptococci, a group of pathogens associated with dental caries, have remained similar in children with and without caries. This implies that good dental health is possible in the presence of high prevalence of mutans streptococci, but raises speculation that the decrease in dental caries, may be caused by a change in virulence of these strains. It is also unclear if these bacterial strains are acquired through inter-familial transmission or genetically altered by influences from the oral environment. This thesis reports the first studies of gene expression and bacterial virulence in relation to traditional African-foods using clinical isolates from South African children. To establish the source of transmission, the phenotype and genotype of mutans streptococci strains from 31, five-year-old black, and coloured, children and their mothers living in Gauteng were characterized. The children were examined for caries, and plaque and salivary samples collected from both the children and their mothers. Samples were selectively cultured for mutans streptococci, biochemically differentiated and the genetic diversity of these isolates determined by PCR-RFLP of the gtfB and gtfI glucosyltransferase virulence genes. Phenotyping showed that Streptococcus mutans were 90% (155/172) prevalent, but the detection of Streptococcus sobrinus was low and comprised 10% (17/172) of the remaining vii isolates. Twenty-six percent of S. mutans clinical isolates (41/155) did not metabolise melibiose and the gtfA gene encoding for the uptake of this sugar was absent in 26 of the 41 melibiose-negative strains. GtfB gene polymorphisms in S. mutans clinical isolates from the two ethnic populations and from caries-free and caries-active 5-year-old children were similar (Principal Components Analysis). However high genetic diversity was observed in S. mutans isolates, with 23 different gtfB amplitypes shown by PCR-RFLP analysis. Sixteen different gtfI amplitypes were indicated in S. sobrinus clinical strains. The percentage match between gtfB amplitypes (HaeIII enzyme digests) in the children and their mothers ranged from 3% to 9% in caries-free children and caries-active children, respectively. Identical gtfB amplitypes from melibiose-negative phenotypes were shared by four mothers and their children only. To determine the growth and virulence response of the variant mutans streptococci genotypes, six laboratory reference strains (NCTC) and five, clinical isolates were challenged to traditional African staple foods and food combinations. The bacteria were exposed in batch culture for 16 hours to maize, samp, brown bread, maize+milk+sugar, maize+gravy, samp+beans, brown bread+margarine+peanut butter, 3% sucrose and a synthetic complex medium, BHI+3% sucrose. Results showed that growth was slow in maize (5.6 h) and samp (5.7 h) indicated by the long doubling time and the low number of generations (g = 4.2; g = 3.6). Sufficient lactic and acetic acid was produced to drop the pH to below 5.7, the ‘critical’ level for enamel demineralisation during the fermentation of brown bread (5.37), bread+margarine+peanut butter (5.51) and 3% sucrose (5.32). Water-insoluble extracellular polysaccharides produced was significantly lower (P<0.05) in samp and maize and viii maize+milk+sugar, with most residual glucose found in BHI + 3% sucrose (1.61±0.52 mg/mL) and maize+gravy (0.51±0.61 mg/mL). Mean concentrations of extracellular protein ranged from a low of 0.015±0.007 mg/mL in samp+beans to a high of 0.29±0.16 mg/mL in BHI + 3% sucrose. The inherent pH of individual foods closest to neutral was: milk (7.0) beans (6.07), samp (6.20), maize (6.82) and peanut butter (6.90). However, beans (5.7×10 G3 [H%]), milk (5.1 ×10G3 [H ]) and peanut butter (4.0×10 [H ]) showed more efficient buffering, which in combination % G3 % with other food components, raised the inherent buffering capacity of the food. These mixed foods required a larger quantity of acid to be produced by bacterial metabolism to lower the pH to 5.7. A preliminary study on the effect of single foods on S. mutans gtfB gene expression showed that mRNA gtfB transcripts were mostly inhibited in clinical isolates, but not in reference strains. The gtfI gene of all S. sobrinus test strains was expressed in 3% sucrose and BHI+3% sucrose, but the response differed in the remaining foods.The statistically significant association shown between mutans streptococci phenotype, gtf gene expression and the food challenge (P<0.0001), verifies that expressed phenotypic characteristics is dependent on gene expression. The results presented in this thesis show that a high diversity of gtf genes exists in mutans streptococci clinical isolates from South African black African, and coloured, 5-year-old children and their mothers. However, no specific genotype was unique either to dental status or ethnic population, with children acquiring genotypes from other points of contact besidesthe mother. Furthermore, the growth and virulence response (acidogenesis, water-insoluble ECP) of S. mutans and S. sobrinus genotypes and reference strains are subject to the dietary nutrients available. The inherent buffering capacity of maize, samp, maize+milk+sugar, maize+gravy and samp+beans, coupled to a low sucrose content, make these foods non-caries promoting, but the ability of test bacteria to remain viable on these nutrients, indicate that the mutans streptococci have a natural adaptive ability to assimilate other nutrients as a source of carbon when sucrose is limited. The control of gtfB and gtfI gene expression by traditional African foods suggests that virulence of the mutans streptococci are influenced more by the dietary environment than by genotype. Also, the difference in virulence properties between clinical and laboratory reference strains indicate an attenuation in virulence of wild-type strains.

Clostridium perfringens é um dos microrganismos mais freqüentemente envolvidos em surtos de enfermidades transmitidas por alimentos. Este microrganismo pode ser classificado em cinco tipos toxigênicos (A-E), de acordo com a detecção dos genes codificadores de suas principais toxinas: alfa (cpa), beta (cpb), épsilon (etx) e iota (iap), sendo que técnicas moleculares empregando a PCR são atualmente utilizadas para genotipagem desses isolados. Alguns isolados de C. perfringens produzem uma enterotoxina (CPE) que é responsável pelos sintomas clínicos desenvolvidos em casos de toxinfecção alimentar, sendo que esta toxina é codificada pelo gene cpe. A simples detecção de C. perfringens em um alimento, mesmo naqueles suspeitos de causar surtos, não é suficiente para considerá-lo como de risco à saúde do consumidor. Isto porque dentre os isolados de C. perfringens apenas um número muito pequeno apresenta o gene cpe. Além disso, isolados de C. perfringens não produtores de CPE estão amplamente disseminados no ambiente, em alimentos e mesmo em fezes de pessoas. Desta forma, com o presente estudo verificou-se a freqüência de C. perfringens dentre isolados de clostrídios sulfito redutores, a freqüência de C. perfringens potencialmente enterotoxigênicos e sua variabilidade genética, de modo a evidenciar a importância dessas cepas como causadoras de doenças, além de fornecer subsídios para melhorar os conhecimentos sobre as características das cepas circulantes em nosso meio. Foram utilizados 335 isolados de clostrídios sulfito redutores provenientes de alimentos (126), solo (84) e fezes de animais (125). Dos 335 isolados, 146 (43,6%) foram caracterizados, através de reações bioquímicas e moleculares, comoC. perfringens, sendo 75 isolados (59,5%) provenientes de alimentos, 43 (51,2%) de solo e 28 (22,4%) de fezes de animais. Todas as cepas de C. perfringens analisadas foram tipadas como C. perfringens tipo A. Dos 75 isolados de C. perfringens provenientes de alimentos, 20 apresentaram o gene cpe, sendo 13 (65%) com localização cromossomal; nas demais cepas não foi possível determinar sua localização. Nos isolados de C. perfringens provenientes de solo e das fezes de animais não se verificou a presença desse gene. Das 20 cepas de C. perfringens que apresentaram o gene cpe detectou-se em 15 a produção de enterotoxina; as cinco cepas restantes não apresentaram esporulação no meio DUNCAN STRONG modificado, não sendo possível avaliar sua atividade enterotoxigênica. As 146 cepas de C. perfringens quando submetidas à PFGE geraram 69 perfis PFGE distintos, sendo 42 exclusivos para uma única cepa, indicando uma grande variabilidade genética, entre isolados provenientes de amostra de alimentos, fezes ou solo. A utilização de clostrídios sulfito redutores, ou mesmo de C. perfringens como indicador de possível risco à saúde dos consumidores pode levar à condenação desnecessária de alimentos, uma vez que existe baixa correlação entre costrídios sulfito redutores e C. perfringens, independente da fonte de isolamento, além da baixa freqüência do gene cpe nas cepas estudadas. / Clostridium perfringens is one of the most frequently microorganism involved in outbreaks of foodborne diseases. This microorganism can be classified into five toxigenic types (A to E), according to the detection of genes encoding its major toxins: alpha (cpa), beta (cpb), epsilon (etx) and iota (iap). Molecular techniques using PCR are currently used for genotyping this isolates. Besides the major toxins, some isolates of C. perfringens produce an enterotoxin (CPE) that is responsible for clinical symptoms developed in cases of food poisoning. This enterotoxin is encoded by the cpe gene. The simple detection of C. perfringens in food, even in those suspected of causing outbreaks, is not enough to consider it as a risk to consumers´ health. This happens because among the isolates ofC. perfringens only a very small number shows the cpe gene. In addition, isolates of C. perfringens that do not produce CPE are widespread in the environment, food and even in feces of humans. Thus, the present study examined the frequency of C. perfringens isolates among sulfite reducing clostridia, the frequency of potentially enterotoxigenic C. perfringens and its genetic variability in order to highlight the importance of these strains in causing diseases, and provides subsidies to improve the knowledge about the strains that are circulating in our environment. A total of 335 isolates of sulfite reducing clostridia from foods (126), soil (84) and animal feces (125) were used. Among the 335 isolates, 146 (43.6%) were characterized by biochemical and molecular reactions as C. perfringens, being 75 (59.5%) from foods, 43 (51.2%) from soil and 28 (22.4%) from animal feces. All strains of C. perfringens were typed as C. perfringens type A. Of the 75 isolates of C. perfringens from food, 20 had the cpe gene, and in 13 (65%) the gene was chromosomally located. In the other strains it was not possible to determine the location of this gene. In isolates of C. perfringens from soil and animal feces the cpe gene was not present. Amongst the 20 strains of C. perfringens positive for cpe, enterotoxin production was detected in 15. Five strains showed no sporulation in the medium modified Duncan Strong, being not possible to verify their enterotoxigenic activity. All C. perfringens were subjected to PFGE and generated 69 different PFGE profiles, being 42 unique to a single strain, indicating a great genetic variability among isolates from food, feces or soil. The use of sulfite reducing clostridia, or even C. perfringens as an indicator of possible health risk to consumers can lead to unnecessary condemnation of food, since there is low correlation between sulfite reducing clostridia and C. perfringens, regardless of source of isolation. This study also shows a low frequency of cpe gene in the strains indicating the low risk in causing foodborne disease.

Populações naturais de Tabebuia cassinoides Lam (DC) vem sedo intensivamente exploradas a mais de 70 anos, sendo que atualmente restam poucas populações em condições de exploração comercial. Contudo, a pressão para a contínua exploração das populações remanescentes permanece, embora estudos recentes venham indicando que a intensidade de exploração adotada está causando forte perda de diversidade genética. Assim, o objetivo deste trabalho foi estudar os impactos do manejo nos níveis de diversidade genética de populações naturais de T. cassinoides, usando dados de isoenzimas de amostras de árvores adultas de sete populações, sendo quatro naturais e três manejadas, procedentes do Vale do Ribeira-SP. Foram amostradas aproximadamente 60 árvores por populações, com exceção de uma população, onde foram amostradas 100 árvores e medido o diâmetro a altura do peito (DAP) de cada árvore. Os efeitos do manejo foram avaliados simulando-se diferentes intensidades de desbaste em função de classes de DAP e retenção de diferentes tamanhos populacionais por hectare (20, 30, 50, 75 e 100 genótipos). Os diferentes cenários foram avaliados comparando-se os índices porcentagem de locos polimórficos (), número médio de alelos por locos (), heterozigosidade observada () e esperada em equilíbrio de Hardy-Weinberg () e índice de fixação (). A estrutura genética espacial intrapopulacional de cinco das sete populações foi estuda amostrando-se 12 a 20 grupos aleatórios, formados pelas cinco árvores mais próximas. Em cinco populações as coordenadas geográficas das árvores amostradas foram registradas (usando GPS) para o estudo da distribuição espacial dos genótipos. T. cassinoides apresenta altos níveis de diversidade genética (=3,1; =0,455; =0,445) quando comparada a outras espécies arbóreas tropicais. Comparando as médias das populações naturais e manejadas, foram detectados maiores níveis de diversidade genética nas populações naturais (=2,64; =0,491; =0,504), relativamente as manejadas (=2,29; =0,406; =0,353). A maior parte da diversidade genética encontra-se dentro das populações (mínimo 27,6%). Nas populações naturais, 12,8% da diversidade genética encontra-se entre populações e nas manejadas e 28,4%. Dentro das populações naturais, 12,3% da diversidade genética encontra-se entre grupos e nas manejadas 9,7% encontrava-se entre grupos, sugerindo que a coancestria média dentro das populações aproxima-se da esperada em meios-irmãos (0,125) e, portanto, que existe estrutura genética espacial nas populações de T. cassinoides. Igualmente, a análise da distribuição espacial dos genótipos por autocorrelação espacial detectou indícios significativos de estruturação genética espacial até a distância aproximada de 50 m de raio. Na estimativa dos índices de diversidade genética para cinco classes diamétricas não foram detectadas correlações significativas entre as classes diamétricas e os índices e . Contudo, associações significativas foram detectadas entre as classes diamétricas e os índices (AˆoHˆeHˆfˆAˆeHˆoHˆAˆeHˆoHˆAˆeHˆoHˆAˆeHˆoHˆrˆ=0,813) e (fˆ910,0ˆ&#8722;=r), sugerindo que árvores de maiores classes diamétricas apresentam maiores heterozigosidades e existe provável seleção para heterozigotos. Simulando a retenção de diferentes tamanhos amostrais por hectares, observou-se que todos os parâmetros genéticos foram afetados e que é necessário reter aproximadamente 75 árvores por hectare para que os efeitos negativos em relação à população base sejam baixos. / Natural populations of Tabebuia cassinoides Lam (DC) have been intensively harvested in the last 70 years. The pressure for continuum exploitation of remaining populations remains, although few populations remain in conditions that allow commercial exploitation and recent studies indicated that intensive harvest causes strong loss of genetic diversity. Thus, the objective of this work was to study the impacts of harvesting on genetic diversity levels of T. cassinoides natural populations from Vale do Ribeira-SP, Brazil, using isozymes markers. We collected leaf tissues of adult trees from seven populations, four natural and three harvested. Sixty trees were sampled per population, with the exception of one population, where we sampled 100 trees and also measured their diameter at breast height (DBH). The effects of harvest were evaluated by simulating different logging intensity in this one population, considering several DBH classes and retaining different populational sizes per hectare (20, 30, 50, 75 and 100 remaining trees). The different resulting pictures were evaluated comparing the indexes of the percentage of polymorphic loci (), the mean numbers of alleles per locus (), observed () and expected in Hardy-Weinberg heterozigosity () and the fixation index (). The intrapopulational spatial genetic structure was studied in five of the seven populations, sampling 12 to 20 random groups, formed by the five nearest trees. In order to study the spatial genetic structure, we registered, with the use of GPS, the geographic coordinates of the sampled trees in five populations. The results showed that T. cassinoides has high levels of genetic diversity (=3.1; =0.455; =0.445) when compared with other tropical tree species. By comparing the mean values found for the natural and for the harvested populations, we detected higher levels of genetic diversity in natural populations (=2.64; =0.491; =0.504), relatively to the harvested ones (=2.29; =0.406; =0.353). The largest part of the genetic diversity was found within population (minimum 27.6%). In natural populations, 12.8% of genetic diversity was found among populations and 28.4% on the harvested ones. Within natural populations, 12.3% of genetic diversity was found among groups and 9.7% in the harvested ones, suggesting that the mean coancestry within population is close to the expected in half-sibs (0.125) and, thus, that there is spatial genetic structure in T. cassinoides populations. The analysis of genotypes spatial genetic structure by spatial autocorrelation detected a significant indication for spatial genetic structure at approximately 50 meters distance radius. The genetic diversity index estimation for five diametric classes did not detect significant correlations among diametric classes and and indexes. However, significant associations were detected among the diametric classes and (fˆAˆeHˆoHˆAˆeHˆoHˆAˆeHˆoHˆAˆeHˆoHˆrˆ=0.813) and (fˆrˆ=-0.910) indexes, suggesting that trees of the higher diametrical classes have higher heterozigosity and, thus, preferential selection for heterozygous. When simulating the retention of different sample sizes per hectare, we observed that all genetic parameters were affected and that, in order to maintain low negative effects, it is necessary to retain approximately 75 trees per hectare.