Overuse of conventional antibiotics has led to increased multidrug resistant micro-organisms. Therefore, development of alternative drugs with new mechanisms of action in the control of resistant micro-organisms is urgently needed. Defensins, one of the larger groups of naturally occurring antimicrobial peptides (AMPs), found in a variety of species, may serve as templates for the development of novel therapeutic agents. The work completed in this study is based on an antimicrobial peptide (AMP), Os, derived from the C-terminus of a tick Ornithodoros savignyi defensin isoform 2 (OsDef2). OsDef2 was found to be active against Gram-positive bacteria only, whereas Os, showed bactericidal activity towards both Gram-positive and Gram-negative bacteria. In this study a series of synthetic shorter peptides, based on the sequence of Os, was utilised in order to determine whether shorter peptides would retain their antibacterial activity and selectivity. Initial screening indicated that only two fragments, Os(3-12) and Os(11-22), were active towards the tested Gram-negative and Gram-positive bacteria. The minimum bactericidal concentrations (MBCs) of the two fragments were determined and ranged from 30 μg/ml to 120 μg/ml. The MBCs of the parent peptide, Os (1.88 to 15 μg/ml), was considerably lower than that of Os(3-12) and Os(11-22). As previously observed for Os, neither of the peptides showed cytotoxic effects towards eukaryotic cells. The amidated analogue of one of the active peptides, Os(11-22)NH2, was further evaluated in terms of its secondary structure, antibacterial and antioxidant activities as well as cytotoxicity. Amidation increased the activity of Os(11-22) 16 fold towards B. subtilis (MBC of 1.88 μg/ml) and 32 fold towards both Escherichia coli and Pseudomonas aeruginosa (MBC of 3.75 μg/ml), whereas a 2 fold decrease in activity was observed against Staphylococcus aureus (MBC of 60 μg/ml). Circular dichroism data showed that amidation altered the secondary structure of Os(11-22) from α-helical to mostly random coiled. In the presence of 30% serum the activity of Os(11-22)NH2 unexpectedly increased 8 fold against S. aureus (MBC of 7.5 μg/ml), but decreased 32 fold against E. coli (MBC of 120 μg/ml). The activity of Os(11-22)NH2 in 100 mM NaCl decreased 4 fold against E. coli (MBC of 15 μg/ml), but was completely lost (MBC >120 μg/ml) against S. aureus. The kinetics of bactericidal activity indicated that Os(11-22)NH2 killed B. subtilis and E. coli within 30 min and 120 min, respectively, whereas Os killed both bacteria within 5 min. Even at high concentrations Os(Os(11-22)NH2 was non-toxic towards human erythrocytes and SC-1 cells, moreover an increase in SC-1 cell number was observed at 120 μg/ml. The peptide showed strong antioxidant activity and was found to be 4 fold more active than glutathione (GSH), however Os was 3.4 fold more antioxidative than Os(11-22)NH2. Os(11-22)NH2 can be considered a dual functional peptide, since it possesses both antibacterial and antioxidant activity. The amidated peptide has the potential for use against the damaging effects of oxidative stress associated with infectious diseases and recovery of chronic wounds. Further investigation into structure-function properties of Os(11-22)NH2 is necessary. / Dissertation (MSc)--University of Pretoria, 2013. / gm2014 / Biochemistry / Unrestricted

Thesis (MBA (Business Management))--University of Stellenbosch, 2007. / ENGLISH SUMMARY: Fossil fuel has been the preferred source for the production of transportation fuel for many years. However, this is not a renewable resource. Many conflicting reports have been published as to how long this resource will last. One thing is certain: eventually the supply of cheap crude oil will run out. It is therefore crucial to start the search for renewable alternatives now. There are a number of possible candidates vying for replacing fossil fuel as primary transportation fuel. Hydrogen, methanol, biodiesel and bioethanol all have the characteristics required of a good transportation fuel. It is unlikely that only one of these will replace oil. A more likely scenario would be that they all play a role in transportation in the future. Apart from being renewable, these alternatives have the further advantage of being less damaging to the environment, something that will become essential in future. Among the renewable alternatives, bioethanol has the second highest energy density. Currently, ethanol production worldwide almost exclusively uses sugarcane and maize as raw material. However, both these are food crops and using them for ethanol could lead to an increase in food prices. Furthermore, there is not enough agricultural land available to produce sufficient quantities of sugarcane and maize for ethanol to replace fossil fuel. Producing ethanol from plant material has the potential to meet the capacity requirements without impacting directly on food production. Approximately 180 million tons of agricultural biomass are produced in the United States each year, sufficient to produce 75 to 110 billion litres of ethanol. Despite its abundance, the technical challenges in converting cellulose to ethanol are significant. One major obstacle to the production of ethanol out of plant material is that most of the sugar in plant material is unavailable for fermentation by micro-organisms. In order to render the sugars in the cellulose fraction accessible to conversion, it is necessary to treat the plant fibres with a combination of chemical and enzymatic processes. Only when a complex mixture of enzymes is used, does it become possible to break down cellulose to glucose for subsequent fermentation to ethanol. Biomass processing by means of enzymes currently involves four separate biological steps: (i) production of enzymes (cellullases and hemicellulases), (ii) hydrolysis of cellulose and hemicellulose to sugars, (iii) fermentation of hexose sugars and (iv) fermentation of pentose sugars. Consolidated BioProcessing (CBP) will combine all these steps into one. However, CBP is not yet possible and the magnitude of research and developmental advancement required to realize this goal is significant. Both sugar and starch ethanol technologies are well established and major process advances are therefore unlikely. Currently there are no commercial-sized plants for the production of ethanol from lignocellulosics, however this is likely to change in the near future considering the progress made in this field during recent years. This study will focus on the current status of the bioethanol industry, as well as on the potential for future development. / AFRIKAANSE OPSOMMING: Fossielbrandstof was vir baie jare die hoofbron vir die produksie van brandstof vir die vervoerbedryf. Fossielbrandstof is nie ’n hernubare energiebron nie en daar is al baie gespekuleer oor presies hoe lank daar nog goedkoop olie beskikbaar sal wees. Baie min van die gepubliseerde bronne stem ooreen, maar almal is dit eens dat olie op een of ander stadium sal opraak. Om hierdie rede is dit noodsaaklik om nou reeds te soek na alternatiewe. Daar is ’n hele aantal hernubare alternatiewe wat gebruik kan word in die plek van olie. Waterstof, metanol, biodiesel en bioetanol beskik almal oor die nodige eienskappe om ’n effektiewe vervoerbrandstof te wees. Die hoofvoordeel van hierdie brandstowwe is dat hulle minder skadelik is vir die omgewing as olie, ’n eienskap wat baie belangrik sal wees in die toekoms. Die kans is eger skraal dat een van bogenoemde bronne die mark totaal sal oorheers soos wat olie tot op hede oorheers het. ’n Meer waarskynlik uitkoms sou wees dat al hierdie bronne op een of ander manier ’n rol gaan speel in die vervoerbedryf in die toekoms. Etanol het die tweede hoogste energie digtheid van die vier genoemde hernubare brandstowwe. Etanol word tans uitsluitlik van suikerriet en mielies geproduseer. Beide suikerriet en mielies is voedselgewasse en die gebruik daarvan vir brandstof kan lei tot ’n toename in voedselpryse. Daar is ook nie genoeg landbougrond beskikbaar vir die verbouing van suikerriet en mieles sodat genoeg etanol geproduseer kan word om fosielbranstof te vergang nie. Die vervaardiging van etanol vanaf lignosellulose het die potensiaal om etanolkapasiteitprobleme te oorkom sonder om direk met voedselproduksie te kompeteer. Ongeveer 180 miljoen ton landbouafval word jaarliks in die Verenigde State geproduseer, genoeg vir die vervaardiging van tussen 75 en 110 biljoen liter etanol. Die tegniese kompleksiteit gekoppel aan die omskakeling van sellulose na etanol is beduidend. Die belangrikste hindernis vir die produksie van etanol vanaf plantmateriaal is die feit dat die meeste van die suiker nie beskibaar is vir fermentasie deur mikroörganismes nie. Plantvesels moet daarom met ’n kombinasie van chemikalieë en ensieme behandel word om sodoende die suiker beskikbaar te maak vir omskakeling. Sellulose kan slegs met ’n komplekse mengsel van ensieme afgebreek word tot glukose wat dan daarna gefermenteer kan word tot etanol. Die verwerking van biomassa met behulp van ensieme behels tans vier afsonderlike biologiese stappe: (i) ensiemproduksie (sellulases en hemisellulases), (ii) hidrolise van sellulose en hemisellulose tot fermenteerbare suikers, (iii) fermentasie van heksose suikers en (iv) fermentasie van pentose suikers. Consolidate BioProcessing (CBP) poog om al vier hierdie stappe te kombineer. Ongelukkig is die CBP proses nog nie moontlik nie en daar moet nog baie navorsing en ontwikkeling gedoen word om dit ’n realiteit te maak. Beide die metodes vir suiker- en styseletanolproduksie is goed gevestig, dus is die kans vir beduidende verbeteringe klein. Daar is tans geen aanlegte van kommersiële grootte vir die produksie van etanol vanaf lignocellulose nie, maar dit gaan waarskynlik binnekort verander as ’n mens die vordering in ag neem wat daar onlangs gemaak is in hierdie veld. Hierdie studie fokus op die huidige stand van sake in die etanolbedryf en die ontwikkelingsmoontlikhede vir die toekoms.

In this study, two symbiotic fungi of Southern Pine Beetle (SPB), Entomocorticium peryii and Entomocorticium sp.A were evaluated in terms of polyphenol oxidase (PPO) production. The effect of different inhibitors, inducers and assay parameters such as temperature and pH on enzyme activity were investigated and maximum PPO activity was observed at 30&deg / C, pH 8.0 and when tannic acid was used as an inducer. Copper-chelator salicyl hydroxamic acid (SHAM) and pcoumaric acid, both indicated as inhibitors of tyrosinase and catechol oxidase significantly reduced the activity. For biochemical characterization studies, the enzyme was concentrated by ultrafiltration. To determine type of the enzyme, activity staining after Native-PAGE was carried out. Type of polyphenol oxidase produced by E. peryii and E. sp.A was determined as catechol oxidase by activity staining. However higher activity was observed on hydroquinone (p-diphenol) rather than catechol (o-diphenol). The enzyme obeys Michealis-Menten kinetics with Km and Vmaxvalues being 10.72 mM hydroquinone and 59.44 U/ml for E. peryii and 8.55 mM hydroquinone and 73.72 U/ml for E. sp.A respectively..

Fresh produces, fruit juices and herbal teas used in our regular diet may have importance in the protective treatment of some infectious diseases. In this study, dietary produces were investigated for their antioxidant activities and antimicrobial activities against group A &szlig / -haemolytic streptoccoci. Streptococcus pyogenes, a member of the group A &szlig / -haemolytic streptococci, is a very dangerous pathogen, which may cause diseases such as tonsillopharyngitis, meningitis, rheumatic arthritis. Fruits and vegetables / onion, radish, carrot, plum, fruit juices / orange, peach, pomegranate, grape and teas / sage, anise, rosehip, chamomile were chosen as samples of regular daily diets. Dry extracts were obtained either by lyophilizing or fractionating in ethyl acetate. Antioxidant activities of extracts were examined by total phenolic content determination, and 2,2-diphenyl-1-picrylhydrazyl radical scavenging (DPPH) methods. Antimicrobial activities of extracts were studied by disk diffusion test, minimum inhibitory and bactericidal concentration methods. Sage, plum, onion and radish displayed high radical scavenging activity with EC50 values of 0.043, 0.049, 0.148 and 0.414 mg/mL, respectively. Plum, sage, onion and radish were found high in total phenolic contents with &amp / #956 / g gallic acid equivalent of 50.506, 48.299, 44.427 and 13.135 in mg extract, respectively. High antimicrobial activities were obtained by onion, radish, anise, carrot and peach extracts as tested by disk diffusion method with respective 20, 16, 16, 14 and 14 millimeters clear growth inhibition zones. Carrot, onion and radish extracts were found as effective bacteriostatic and bactericidal agents with minimum inhibitory and bactericidal respective concentrations of 0.008, 0.125, 0.250 mg/mL and 0.06, 0.5, 1 mg/mL.

Although traditional microbiological methods are accepted standard for Salmonella detection, they are labor intensive and time consuming. Therefore, for food industry and public health, finding sensitive and rapid methods is required. As a rapid and reliable tool, Real-Time PCR is one of the most common methods in molecular detection and research area. The aim of the current study is to develop rapid, sensitive and quantitative Salmonella detection method using Real-Time PCR technique based on inexpensive, easy to produce, convenient and standardized plasmid based positive control for the first time. To achieve this, two plasmids were constructed as reference molecules by cloning two most commonly used Salmonella specific target regions &lsquo / invA and ttrRSBC&rsquo / into them. Standard curves were constructed for the plasmids and reproducibility, PCR efficiency, amplification efficiency values were calculated. To illustrate the applicability of the developed method, enriched (as used commonly for Salmonella detection with Real-Time PCR) 105 to 100 CFU/ml level (estimated by standard plate counts before enrichment) S. Typhimurium ATCC 14028 cultures were tried to detect and quantify, also compared with traditional culture method. In addition, detection limits of the developed technique were determined by serial dilution of DNA extracted from 105 CFU/ml level. The results revealed much faster detection ability of the developed plasmid based Salmonella detection method (in comparison to traditional culture method, ISO 6579:2004) allowing quantitative evaluation with perfect reproducibility, sensitivity (except for lower concentrations for invA target), detection limit, PCR efficiency, amplification efficiency for both invA and ttrRSBC targets. The detection and quantification ability of the method developed by using S. Typhimurium ATCC 14028 cultures were tested also with 15 Salmonella species using milk as a representative food. The results also revealed much faster (in comparison to traditional culture method, ISO 6579:2004) quantitative detection ability of the developed method. Thus, the developed method has great potential to be used in food industry for rapid and quantitative Salmonella detection.

Globally, investigations into food-borne illnesses show that the majority of cases involve poor hand hygiene of the food handler. The challenge of providing safe food therefore requires new strategies for evaluating cross-contamination of pathogenic micro-organisms on the food handler's hands, which might be detrimental or hazardous to the health of the patient Although food-borne diseases may be multifactorial in aetiology, no standards or evaluation systems, such as an occupational health surveillance programme, are available to monitor and ensure that food is free of pathogens. The formulation and implementation of standards may contribute to ensuring that food handlers comply with hand hygiene practices during food handling. Such practices guarantee that food reaching the patient is safe. The objectives in this research project originated from the occupational health practice and gave direction of the empirical research project. The literature was reviewed to discover what is currently known concerning the food handlers' hand hygiene during food handling and food-borne illnesses and the theoretical framework gave direction and guidance to the survey design of the empirical research, which was quantitative, explorative, descriptive and contextual in nature. The food handlers from the food preparation sections of the four major healthcare services in Potchefstroom, in the North West Province, South Africa, were the target population and the sampling method was all-inclusive (n=110). Eighty (75.47%) food handlers participated in the research project. The design entailed three steps. The first was conducted with a questionnaire, to identify the food handlers' compliance with hand hygiene during food handling. The second step involved determining the prevalence of Escherichia coli and Staphylococcus aureus on the food handlers' hands. The results were used for the formulation of standards for the hand hygiene of food handlers. Finally, recommendations for practice, education and research were made. The implementation of these recommendations could contribute knowledge to the body of nursing and promote good hand hygiene practices in the healthcare service. / Thesis (M.Cur.)--North-West University, Potchefstroom Campus, 2009.

Globally, investigations into food-borne illnesses show that the majority of cases involve poor hand hygiene of the food handler. The challenge of providing safe food therefore requires new strategies for evaluating cross-contamination of pathogenic micro-organisms on the food handler's hands, which might be detrimental or hazardous to the health of the patient Although food-borne diseases may be multifactorial in aetiology, no standards or evaluation systems, such as an occupational health surveillance programme, are available to monitor and ensure that food is free of pathogens. The formulation and implementation of standards may contribute to ensuring that food handlers comply with hand hygiene practices during food handling. Such practices guarantee that food reaching the patient is safe. The objectives in this research project originated from the occupational health practice and gave direction of the empirical research project. The literature was reviewed to discover what is currently known concerning the food handlers' hand hygiene during food handling and food-borne illnesses and the theoretical framework gave direction and guidance to the survey design of the empirical research, which was quantitative, explorative, descriptive and contextual in nature. The food handlers from the food preparation sections of the four major healthcare services in Potchefstroom, in the North West Province, South Africa, were the target population and the sampling method was all-inclusive (n=110). Eighty (75.47%) food handlers participated in the research project. The design entailed three steps. The first was conducted with a questionnaire, to identify the food handlers' compliance with hand hygiene during food handling. The second step involved determining the prevalence of Escherichia coli and Staphylococcus aureus on the food handlers' hands. The results were used for the formulation of standards for the hand hygiene of food handlers. Finally, recommendations for practice, education and research were made. The implementation of these recommendations could contribute knowledge to the body of nursing and promote good hand hygiene practices in the healthcare service. / Thesis (M.Cur.)--North-West University, Potchefstroom Campus, 2009.

Suite à des usages intensifs d’origines industrielles, des surfaces considérables de sols dégradés, peu fertiles, voire contaminés sont délaissées. Dans un contexte de raréfaction des sols et de pressions foncières et économiques grandissantes, la réhabilitation de ces sols fortement anthropisés et délaissés peut-être un enjeu. Toutefois, pour envisager une réutilisation de ces sols, il est nécessaire de mieux les caractériser. L’étude de la qualité des sols prend rarement en compte la biodiversité et le fonctionnement biologique. Ainsi, l’objectif de ce travail de thèse était de caractériser des sols délaissés, en prenant en compte leurs paramètres abiotiques, biotiques et fonctionnels. Pour cela, six sols fortement anthropisés délaissés du nord-est de la France, correspondant à différentes activités industrielles, ont été étudiés in situ et en laboratoire. Plusieurs groupes biotiques (bactéries, champignons, mésofaune, macrofaune et flore) ont été étudiés afin d’avoir une approche quasi-exhaustive de la biodiversité des sols. Une approche taxonomique et fonctionnelle (basée sur les traits) de la biodiversité a été réalisée pour les champignons, la méso- et la macrofaune. De plus, l’évolution in situ au cours du temps des paramètres abiotiques et biotiques a été prise en compte sur un des six sols délaissés étudiés. Enfin, les interactions biotiques entre une espèce de collembole, de champignon mycorhizien à arbuscules et de plante herbacée ont été étudiées dans deux sols délaissés, en laboratoire. Nous avons montré que les sols délaissés étaient caractérisés par une biodiversité significative, comparable selon les cas, à celles d’autres types de sols, comme les sols forestiers, de prairies ou agricoles. Toutefois, des différences de densité, de richesse et de structures taxonomiques et fonctionnelles entre les sols délaissés existent et dépendent du groupe biotique étudié. Ces différences sont notamment liées aux propriétés physico-chimiques contrastées de ces sols. Ainsi, un sol construit, amendé en compost, était l’écosystème le moins perturbé des sols étudiés, contrairement à un autre sol construit et contaminé en métaux lourds. Nous avons montré que les paramètres physico-chimiques, et surtout biologiques, évoluaient rapidement au cours du temps (environ un an) dans le sol construit contaminé en métaux lourds. Enfin, nous avons mis en évidence, dans les deux sols étudiés en laboratoire, des modifications des interactions biotiques sous l’influence de nombreux paramètres comme le volume de sol, la durée de l’interaction, la présence d’une microflore indigène etc. Finalement, nous avons montré que ces sols pouvaient être le support de services écosystémiques tels que l’habitat pour la biodiversité et qu’ils pouvaient être fonctionnels, permettant ainsi de considérer leur potentielle valorisation / Due to industrial activities intensification, large surfaces of degraded soils, with low fertility and sometimes contamination, are derelict. In the context of land depletion and economic pressure, the rehabilitation of these derelict anthropogenic soils could be a key issue. However, these derelict soils needs to be better characterized before to consider their potential use. Soil quality studies rarely take into account the biodiversity and the biological functioning. Thus, the aim of this PhD work was to characterize derelict soils by considering their abiotic, biotic and functional parameters. To this end, six derelict strongly anthropogenic soils from north-eastern France, resulting from different industrial activities, were studied in situ and in laboratory. Several biotic components (bacteria, fungi, mesofauna, macrofauna and flora) were studied to have an almost complete approach of the soil biodiversity. Taxonomical and functional (trait-based approach) study of biodiversity was performed for fungi, meso- and macrofauna. Moreover, the in situ evolution over time of abiotic and biotic parameters was taken into account in one of the six studied derelict soils. Lastly, biotic interactions between a species of Collembola, of arbuscular mycorrhizal fungi and of herbaceous plant were studied in two derelict soils, in a growth chamber. We showed that derelict soils were characterized by a significant biodiversity, comparable case to case with other kinds of soils like forest, grassland or crop. Nevertheless, differences in terms of density, richness and taxonomical and functional structure community were observed between soils and depend on considered biotic group. These differences were notably linked with contrasting physico-chemical parameters between soils. Thus, a compost-amended constructed soil was the less disturbed among the six studied soils, in contrast with a heavy metal-contaminated constructed soil. We showed that abiotic parameters, notably biotic parameters, evolved quickly (within one year) in the metal-contaminated constructed soil. In the two derelict soils where interactions between Collembola and mycorrhizal fungi were studied, biotic interactions were affected by several parameters like soil volume, time of interaction, indigenous microflora presence etc. Finally, we have shown that these derelict soils support ecosystems services such as biodiversity reserve and could be functional, allowing potential re-use

Ce projet concerne l’analyse de l’organisation de populations microbiennes au sein de structures complexescomme des dépôts ou des biofilms.Si différentes méthodes sont couramment utilisées pour étudier la structure globale ou l’organisation localed’agrégats microbiens, peu d’entre elles, permettent de réaliser simultanément ces deux analyses et nécessitentsouvent des étapes de préparation qui pénalisent un approche in-vivo et en dynamique.La stratégie proposée repose sur la mise en oeuvre de micro-organismes modèles autofluorescents (levures etbactéries) qui peuvent sans aucun traitement être directement observés en microscopie. La similitude ducomportement physiologique de ces micro-organismes avec celui des souches sauvages a été démontrée. Lesconditions d’acquisition des images en microscopie confocale ont été optimisées. Des dispositifs spécifiques ontété conçus pour générer des dépôts ou des biofilms dans des conditions de contraintes physico-mécaniques etbiochimiques maîtrisées afin d’analyser simultanément leurs caractéristiques et les performances du bioprocédé.Ainsi les dépôts ont pu être observés in-vivo et in-situ grâce à une cellule de filtration équipée d’une fenêtred’observation. Le développement d’un biofilm mixte composé de levures et bactéries modèles autofluorescentes,dans un réacteur continu spécifique, a également été analysé par microscopie confocale.Le traitement et les analyses des images acquises au cours des expériences ont été effectués et ont permisd‘étudier la structure globale des agrégats biologiques et l’organisation tridimensionnelle des micro-organismesdans ces structures, en mettant par exemple en évidence une répartition hétérogène de deux populationsmicrobiennes dans des dépôts de filtration ou en comparant la capacité de deux espèces microbiennes à formerdes biofilms en étudiant in-vivo la dynamique de croissance de chacune des espèces.Cette étude a en outre permis de démontrer la pertinence de la méthode proposée, de définir ses limites et sonchamp d’application / The aim of this project deals with the analysis of both the local localization and organization of microbialpopulations in complex structures such as deposits or biofilms. Different methods are currently used to study theglobal structure or the local organization of biological aggregates but only few ones allow a combined approachand require ex-vivo analyses.The proposed strategy uses home-designed model auto-fluorescent microorganisms (yeasts and bacteria) whichcan be observed directly by microscopy without any dying treatment. Same kinetic behaviours between the wildstrains and their recombinant ones were demonstrated. The confocal microscopy conditions were optimised.Specific devices were developed to generate deposits or biofilms under controlled and known hydrodynamic orbiochemical environment conditions to analyse their structure characteristics linked to the bioprocessperformances.Based on the proposed strategy, microbial deposits modifications due to pressure constraints were observed invivo in a specifically designed flow cell equipped with a microscope glass coverslip. A mixed biofilm composedby our auto-fluorescent yeasts and bacteria was carried out in a specific bioreactor allowing the sampling ofbiofilms during their development to be analysed by confocal microscopy. Both studies have shown specificorganisations between yeasts and bacteria mainly depending on their size and on the environment conditions(pressure or dilution rate).These studies of both local and global structure of biological aggregates and 3D-organisation of themicroorganisms within theses structures demonstrated the relevance of the proposed strategy defining the limitsof the method and proposing various perspectives for further characterizations and applications

Made available in DSpace on 2015-03-26T13:23:55Z (GMT). No. of bitstreams: 1 texto completo.pdf: 1952943 bytes, checksum: 5eb0995a9fbd8af8c5b57d51351a7cb1 (MD5) Previous issue date: 2014-07-25 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / The mechanization makes agricultural work less strenuous, more homogeneous farming and increases crop productivity. The system of mechanized tillage directly influence the physical and biological soil properties, in addition to providing appropriate environment for establishment of cultures. Some studies have reported the microbial activity in the soil of the same quality. Microbial activity can be measured by the microbial biomass carbon, soil basal respiration, metabolic quotient and microbial quotient, among others. Tillage can affect the microbial activity because the levels of soil organic carbon can be changed as well as the density, temperature and soil moisture. Several studies using microbiological analyzes for determination of disturbances in agricultural and forestry crops, but the quantification of the interference of tillage, in an isolated form in soil microbial activity is rarely studied. Knowing how much and how tillage impacts on soil microbiota, one can analyze the effects of this process, and seek to mitigate noxious factors, seeking managements best suited to each type of soil and crop systems to be implemented. Thus objective with this study was to evaluate how different systems of mechanized tillage can affect their microbiological activity, evaluating the total organic carbon, microbial biomass carbon, basal soil respiration, metabolic quotient and the quotient soil microbial. The experiment was conducted in an experimental area belongs to the Federal University of Viçosa, was used as treatments for the following types of tillage: No tillage (PD) and conventional tillage (PC) and minimum tillage (CM). The treatments were arranged in a randomized block. The experiment was disposed in a split plot sub subdivided, where the parcels types of tillage systems, subplots depths and in the sub split plots sampling periods in randomized block design with 4 replications causualizados. Data were analyzed by analysis of variance and means were compared using the Tukey test, adopting the 5% level of probability. All analyzes were performed with the aid of SAEG. Microbiological analyzes were conducted at the Laboratory of Organic Matter in Soil, Federal University of Viçosa department. The collections were made in triplicate in two depths, the bands from 0 to 0,10 m from 0,10 to 0,20 m depth. We determined the total organic carbon (COT), microbial biomass carbon (CBM), basal soil respiration (RBS), metabolic quotient (qCO2) and microbial quotient (qMic). The no tillage showed higher levels of microbial biomass carbon and soil basal respiration, in the range 0 0,10 m depth. The values of metabolic quotient were higher in minimum tillage system. The no till was the system that had higher microbial activity in the soil. / A mecanização torna o trabalho agrícola menos árduo, a lavoura mais homogênea e aumenta a produtividade das culturas. O sistema de preparo mecanizado do solo influencia diretamente as propriedades físicas e biológicas do solo, além de propiciar ambiente adequado para estabelecimento das culturas. Alguns estudos relacionam à atividade microbiológica do solo a qualidade do mesmo. A atividade microbiológica pode ser mensurada através do carbono da biomassa microbiano, respiração basal do solo, quociente metabólico e quociente microbiano. O preparo do solo pode interferir na atividade microbiológica, pois os teores de carbono orgânico do solo podem ser alterados assim como a densidade do solo, a temperatura e a umidade do solo. Vários estudos utilizam as análises microbiológicas para determinações de perturbações em culturas agrícolas e florestais, mas a quantificação da interferência do preparo do solo, de forma isolada na atividade microbiana do solo é pouco estudada. Conhecendo-se quanto e como o preparo do solo impacta a microbiota do solo, pode-se analisar os efeitos deste processo, e procurar mitigar fatores nocivos, buscando sistemas de manejos mais adequados a cada tipo de solo e da cultura a ser implementada. Dessa forma objetivou-se com o presente trabalho avaliar como os diferentes sistemas de preparo mecanizado do solo podem afetar a sua atividade microbiológica, avaliando o carbono orgânico total, o carbono da biomassa microbiana, a respiração basal do solo, o quociente metabólico e o quociente microbiano do solo. O experimento foi realizado numa área experimental pertencente à Universidade Federal de Viçosa. Utilizaram-se como tratamentos os seguintes tipos de preparo do solo: plantio direto (PD), Plantio convencional (PC) e cultivo mínimo (CM). O experimento foi disposto em um esquema de parcelas sub subdivididas, tendo nas parcelas os tipos de preparos do solo, nas subparcelas as profundidades e nas sub subparcelas as épocas de amostragem, no delineamento de blocos causualizados com 4 repetições. Os dados foram analisados empregando-se a analise de variância e as médias comparadas utilizando-se o teste Tukey adotando o nível de 5% de probabilidade. Todas as análises foram realizadas com o auxilio do SAEG. As análises microbiológicas foram realizadas no Laboratório de Matéria Orgânica, do departamento de solos da Universidade Federal de Viçosa. As coletas foram realizadas em triplicata, em duas profundidades, nas faixas de 0,0 a 0,10 m e de 0,10 a 0,20 m de profundidade. Foram determinadas o Carbono orgânico total (COT), Carbono da biomassa microbiana (CBM), Respiração basal do solo (RBS), quociente metabólico (qCO2) e quociente microbiano (qMic). O plantio direto apresentou maiores índices de carbono da biomassa microbiana e respiração basal do solo, na faixa de 0,0 - 0,10 m de profundidade. Os valores do quociente metabólico foram maiores no sistema de cultivo mínimo. O plantio direto foi o sistema que apresentou maior atividade microbiológica do solo.