Picophytoplankton were inferior competitors for inorganic phosphorus compared to heterotrophic bacteria. This may be due to the source of energy available for the heterotrophs, while cell-size was of minor importance. However, picophytoplankton were superior to large phytoplankton in the competition for nutrients at low concentrations. Biomass of picophytoplankton was low in brownwater lakes and high in clearwater lakes, compared to the biomass of heterotrophic bacteria. The results suggest that picophytoplankton are inferior to heterotrophic bacteria in the competition for inorganic nutrients in brownwater lakes, where the production of heterotrophic bacteria is subsidized by humic dissolved organic carbon (DOC) Relative to large phytoplankton, picophytoplankton were most important in lakes with intermediate water colour, despite the fact that the lowest nutrient concentrations were found in the clearwater lakes. Large phytoplankton in the clearwater lakes may be able to overcome nutrient competition with picophytoplankton by vertical migration. In conclusion, changes in nutrient content, light availability and concentrations of DOC affect the interactions of heterotrophic bacteria, picophytoplankton and large phytoplankton and are therefore important factors for the structure of the food web in the pelagic zones of lakes. Picophytoplankton (planktonic algae and cyanobacteria, < 2 µm) constitute an important component of pelagic food webs. They are linked to larger phytoplankton and heterotrophic bacteria through complex interactions including competition, commensalism and predation. In this thesis, field and laboratory studies on the competitive ability of picophytoplankton are reported.

This thesis focuses on the interactions among microbiota in clearwater lakes. Field sampling and field experiments were performed to evaluate interactions among microbiota and the importance of benthic versus pelagic microbiota in terms of biomass and production. In addition, carbon cycling in an oligotrophic clearwater lake was calculated. Biomass and production of microbiota was clearly focused to the benthic habitat. During natural nutrient concentrations growth of heterotrophic bacteria (benthic and pelagic) was coupled to production of microphytobenthos in Lake Eckarfjärden, indicating interactions between autotrophic and heterotrophic microbiota in, as well as between, habitats. At increased nutrient concentrations, growth of heterotrophic bacteria was not correlated to microphytobenthos production. This was explained by less release of dissolved organic carbon (DOC) from microphytobenthos when they got access to more nutrients. Further investigations showed different scenarios in oligotrophic clearwater lakes following increased nutrient concentrations. The interactions between microbiota may be altered following increased nutrient concentrations and the microbial mat either positively or negatively affect the pelagic microbiota. The most striking result was that the expected shift towards dominance of pelagic primary production does not necessarily occur. Major flows of carbon were identified between different habitats in the oligotrophic clearwater Lake Eckarfjärden, and the net result was that the benthic habitat provided carbon to the pelagial. High DOC concentrations in the lake together with low pelagic production are factors that would indicate net heterotrophy. Accordingly, the pelagial of Lake Eckarfjärden was net heterotrophic but when the benthic and littoral habitats were included in the calculations, the lake turned out to be net autotrophic. In conclusion, the benthic microbiota contributed significantly to the total production in the investigated lakes and had a major role in the lake metabolism. Thus, this thesis emphasises the importance of benthic microbiota in shallow clearwater lakes.

Within the content of this thesis, it was aimed to understand the changes in the biomass and abundance of heterotrophic bacteria and marine cyanobacteria Synechococcus in time with respect to multitude of ambient physical, chemical and biological factors. For this, monthly samples from discrete depths in the offshore (0-20-40-60-80-100-125-150-175-200 m) and in the near shore (surface and 10 m) stations over a period of one year in the Cilician Basin (eastern Mediterranean) were collected via rosette sampler. Epifluorescent microscope and the image analysis system were used to estimate abundance and biomass of both groups. Coastal station was more abundant and had much higher bacterial (heterotrophic bacteria) and cyanobacterial (Synechococcus) biomass than the offshore station as it receives substantial amount of freshwater from the nearby Lamas River throughout the year. The surface annual averages for bacterial and cyanobacterial abundance and biomass were 9600000 cells/ml - 56.5 microgram C/l and 400000 cells/ml - 24.1 microgram C/l, respectively, at the coastal station. The surface annual averages for bacterial and cyanobacterial abundance and biomass were 8100000 cells/ml &ndash / 49.1 microgram C/l and 210000 cells/ml &ndash / 10.6 microgram C/l, respectively, at the offshore station. Bacterial population always found to exceed Synechococcus abundance within the water column. In general, bacterial and cyanobacterial abundance and biomass tend to decrease with depth. On a seasonal basis, bacterial population was found excessively dominant at the surface or near-surface waters during the second half of the year. Synechococcus were also found more abundant during late summer and autumn. Temperature and nitrate concentration seemed to affect efficiently the abundance of both populations in the area. Based on Spearman Rank Correlation analysis, highly significant correlations between bacterial abundance as well as biomass and ambient temperature were observed at both stations. However, a significant correlation was found between Synechococcus and temperature only at the offshore station. Significant negative correlations are found between nitrate and bacterial abundance and biomass at both stations and between Synechococcus abundance and biomass only at the offshore station. At the offshore station, salinity was also found to be positively correlated with the bacterial and cyanobacterial abundance and biomass.

The eastern Mediterranean has been known as the most oligotrophic water body among the worlds oceans and as a result of limited nutrient inputs from terrestrial sources primary productivity and plankton succession are restricted by lack of nutrients especially by phosphorus and nitrogen. Within this domain, Mersin bay forms a so called hot spot (highly sensitive) area where a sharp contrast exists between the coastal area supplied by land-based nutrient sources and the nutrient limited open sea. Excess nutrient enrichment lead for eutrophication in the inner Mersin bay while altering the quality and quantity of flora from shore to offshore. Microorganisms are highly sensitive and profoundly affected by environmental disturbances and are widely used to assess the impact of environmental changes on ecosystem functioning. With this study, it is aimed to investigate responses of the smaller fractions of phytoplankton composed of heterotrophic bacteria, Synechococcus and flagellates to rapidly changing ambient biological, chemical and physical properties of shelf waters over an extended period between 2008 and 2010. Epiflourescence microscopy and image analysis setup were used to enumerate and measure size of cells for biomass estimates.

Orientador: Adalberto Farache Filho / Banca: Clóvis Wesley Oliveira de Souza / Banca: João Bosco Faria / Resumo: A constante preocupação com a qualidade da água destinada ao consumo, a presença de sabores e odores desagradáveis decorrentes da adição de flúor e cloro nas águas de abastecimento público e a falta de suprimentos adequados de água potável, tem provocado uma contínua demanda por água mineral. A relativa escassez de estudos envolvendo a qualidade microbiológica da água mineral, principalmente na água mineral gaseificada artificialmente, gerou esta pesquisa que tem por objetivo, avaliar e comparar a qualidade bacteriológica de águas minerais sem gás e gaseificadas artificialmente, em embalagens descartáveis, de oito marcas comercializadas em supermercados das cidades de Ribeirão Preto e Araraquara - SP. As duzentos e quarenta amostras analisadas foram divididas em três lotes com cinco unidades gaseificadas e cinco sem gás de cada marca. Foram realizadas análises para determinação de bactérias do grupo coliforme, bactérias heterotróficas e Pseudomonas aeruginosa. Para análise de coliformes totais e E. coli utilizou-se a técnica de substratos cromogênicos, para Pseudomonas aeruginosa utilizou-se a técnica de tubos múltiplos específica e para contagem de bactérias heterotróficas foi utilizada a técnica de cultivo em profundidade. Para as cento e vinte amostras não gaseificadas analisadas (100%), verificou-se a presença de coliformes totais em oito amostras (6,67%), presença de E. coli em seis amostras (5%), presença de Pseudomonas aeruginosa em cinco amostras (4,2%), e 102 amostras (85%) apresentaram contagem de bactérias heterotróficas maior que 500 UFC/mL. Para as cento e vinte amostras gaseificadas analisadas verificou-se que nenhuma delas apresentou contaminações para o grupo coliforme (totais e E. coli) e para Pseudomonas aeruginosa. Apenas três amostras (2,5%) apresentaram contagens superiores a 500 UFC/mL para bactérias heterotróficas... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The constant concern with the water quality reserved to human consumption, the presence of tastes and odors caused by the addition of fluoride and chlorine in public water supplies and the destitution of adequate supplies of potable water has challenged a continuous demand for mineral water. The relative privation of studies on the bacteriological quality of mineral water, mainly in artificially carbonated mineral water generated this project that purpose to value and to compare the microbiological quality of mineral water without gas and carbonated artificially, in dismissible tacking, of eight types, sold in supermarkets in the cities of Araraquara/SP and Ribeirão Preto/SP. The two hundred forty analyzed samples were divided in shares with five unities carbonated mineral water and five without gas. There were put into practice analysis for determination of coliform bacteria, heterotrophic bacteria and Pseudomonas aeruginosa. To analysis of total coliform and E. coli it was used the chromogenic substrates technique, for Pseudomonas aeruginosa used the multiple tube specific technique and to counting heterotrophic bacteria, it was used the technique of growing in depth. To the one hundred twenty samples no carbonated water analyzed (100%), was checked the presence of total coliforms in eight samples (6,67%), presence of E. coli in six samples (5%), presence of Pseudomonas aeruginosa in five samples (4,2%), and one hundred two samples (85%) was with counts above 500 CFU/mL for heterotrophic bacteria. To the one hundred twenty carbonated water samples analyzed (100%), was checked that no samples analyzed was contaminated to the coliform group (total and E. coli) and to Pseudomonas aeruginosa. Just three samples (2,5%) present counts above 500 CFU/mL for heterotrophic bacteria. All the brands of the samples no carbonated water tested (100%) presents out of the specifications of Brazilian legislation in one or more parameters analyzed / Mestre

Made available in DSpace on 2014-06-11T19:29:34Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-12-16Bitstream added on 2014-06-13T20:38:53Z : No. of bitstreams: 1 tebaldi_r_me_arafcf.pdf: 300893 bytes, checksum: dc69e3a75aeeb349d9af75e741a2e2ca (MD5) / Universidade Estadual Paulista (UNESP) / A constante preocupação com a qualidade da água destinada ao consumo, a presença de sabores e odores desagradáveis decorrentes da adição de flúor e cloro nas águas de abastecimento público e a falta de suprimentos adequados de água potável, tem provocado uma contínua demanda por água mineral. A relativa escassez de estudos envolvendo a qualidade microbiológica da água mineral, principalmente na água mineral gaseificada artificialmente, gerou esta pesquisa que tem por objetivo, avaliar e comparar a qualidade bacteriológica de águas minerais sem gás e gaseificadas artificialmente, em embalagens descartáveis, de oito marcas comercializadas em supermercados das cidades de Ribeirão Preto e Araraquara - SP. As duzentos e quarenta amostras analisadas foram divididas em três lotes com cinco unidades gaseificadas e cinco sem gás de cada marca. Foram realizadas análises para determinação de bactérias do grupo coliforme, bactérias heterotróficas e Pseudomonas aeruginosa. Para análise de coliformes totais e E. coli utilizou-se a técnica de substratos cromogênicos, para Pseudomonas aeruginosa utilizou-se a técnica de tubos múltiplos específica e para contagem de bactérias heterotróficas foi utilizada a técnica de cultivo em profundidade. Para as cento e vinte amostras não gaseificadas analisadas (100%), verificou-se a presença de coliformes totais em oito amostras (6,67%), presença de E. coli em seis amostras (5%), presença de Pseudomonas aeruginosa em cinco amostras (4,2%), e 102 amostras (85%) apresentaram contagem de bactérias heterotróficas maior que 500 UFC/mL. Para as cento e vinte amostras gaseificadas analisadas verificou-se que nenhuma delas apresentou contaminações para o grupo coliforme (totais e E. coli) e para Pseudomonas aeruginosa. Apenas três amostras (2,5%) apresentaram contagens superiores a 500 UFC/mL para bactérias heterotróficas... / The constant concern with the water quality reserved to human consumption, the presence of tastes and odors caused by the addition of fluoride and chlorine in public water supplies and the destitution of adequate supplies of potable water has challenged a continuous demand for mineral water. The relative privation of studies on the bacteriological quality of mineral water, mainly in artificially carbonated mineral water generated this project that purpose to value and to compare the microbiological quality of mineral water without gas and carbonated artificially, in dismissible tacking, of eight types, sold in supermarkets in the cities of Araraquara/SP and Ribeirão Preto/SP. The two hundred forty analyzed samples were divided in shares with five unities carbonated mineral water and five without gas. There were put into practice analysis for determination of coliform bacteria, heterotrophic bacteria and Pseudomonas aeruginosa. To analysis of total coliform and E. coli it was used the chromogenic substrates technique, for Pseudomonas aeruginosa used the multiple tube specific technique and to counting heterotrophic bacteria, it was used the technique of growing in depth. To the one hundred twenty samples no carbonated water analyzed (100%), was checked the presence of total coliforms in eight samples (6,67%), presence of E. coli in six samples (5%), presence of Pseudomonas aeruginosa in five samples (4,2%), and one hundred two samples (85%) was with counts above 500 CFU/mL for heterotrophic bacteria. To the one hundred twenty carbonated water samples analyzed (100%), was checked that no samples analyzed was contaminated to the coliform group (total and E. coli) and to Pseudomonas aeruginosa. Just three samples (2,5%) present counts above 500 CFU/mL for heterotrophic bacteria. All the brands of the samples no carbonated water tested (100%) presents out of the specifications of Brazilian legislation in one or more parameters analyzed

Les bactéries et microalgues marines sont acteurs clés du fonctionnement des écosystèmes océaniques et leur contribution dans les cycles biogéochimiques majeurs est largement reconnue. Dans ce contexte, il apparaît essentiel de mieux comprendre les interactions existant entre bactéries et microalgues. Dans l’environnement marin, les interactions spécifiques entre microorganismes nécessitent une forte proximité qui n’est souvent rendue possible que par un attachement cellulaire. La première partie de ce travail de thèse a consisté à sélectionner les microalgues qui présentaient des bactéries physiquement attachées. Deux diatomées appartenant aux genres Thalassiosira et Chaeoceros ont été retenues afin d’étudier leur microflore épibionte issue d’associations à long terme (culture de microalgues établies depuis plusieurs années) et à court terme (microalgues prélevées directement dans l’environnement). Ces travaux ont permis de mettre en évidence une forte ressemblance des communautés épibiontes dans les associations à long terme, qui s’opposait à la forte différence des épibiontes issus des associations à court terme. Les communautés d’épibiontes bactériens étaient majoritairement composées d’alpha- et gammaprotéobactéries, mais aussi de Bacteroidetes et d’actinobactéries. Cette étude a également permis de mettre en évidence que la surface des microalgues représentait un écosystème particulier puisque près de la moitié des épibiontes isolés correspondaient à de nouveaux taxons (genres et espèces). Une de ces souches qui constitue un nouveau genre a été complètement caractérisée, contribuant à l’enrichissement de la diversité bactérienne décrite. Enfin, la nature des interactions entre les deux diatomées et leurs bactéries épibiontes a été analysée par l’intermédiaire de co-cultures, afin d’identifier une interaction forte, qui pourra être examinée par transcriptomique. De très nombreuses interactions commensalismes ont été mises en évidence, reflet de la reminéralisation de la matière organique par les bactéries. Cependant, un faible impact des bactéries sur la croissance des microalgues a été observé. Les conditions expérimentales qui excluent au maximum les stress abiotiques et biotiques, masquent peut-être les interactions qui pourraient se produire dans un environnement naturel plus fluctuant. Ces résultats témoignent de la complexité des interactions biotiques, fournissent des méthodes et des organismes modèles permettant de les étudier et soulèvent de nombreuses hypothèses exaltantes pour les travaux futurs. / Marine microalgal and bacterial contribution to the global biogeochemical cycles is largely recognized and lead to define them as key actors of oceanic ecosystems. In this context, it is essential to better understand the interactions occurring between bacteria and microalgae. In the marine environment, specific interactions between microorganisms require tight physical association that is made possible by cellular attachment. In this work, we first selected microalgae with physically attached bacteria. Two diatoms belonging to the genus Thalassiosira and Chaetoceros were selected to study the epibiotic microflora from long-term (microalgae in culture) and short-term (microalgae directly collected from natural communities) associations. This work highlighted strong similarities between epibiotic assemblages from long-term associations and a higher difference for epibiotic communities from short-term associations. The bacterial epibiotic assemblages were mainly composed of Alpha- and Gammaproteobacteria but also Bacteroidetes and Actinobacteria. This study also highlighted that the surface of microalgae represented a peculiar ecosystem where nearly half isolates constituted new taxa (genera and species). One of them representing a new genus has been completely characterized, contributing to the enrichment of the described bacterial diversity. Finally, the nature of interactions between diatoms and their epibiotic bacteria was analyzed by co-culturing to identify strong interactions, to be further examined by transcriptomics. Numerous commensal interactions have been identified, corresponding to the bacterial remineralization of organic matter. However, only small effects of bacteria on microalgal growth were observed. The experimental conditions that exclude a maximum of abiotic and biotic stresses may mask potential interactions that could occur in an unstable natural environment. These results reflect the complexity of biotic interactions, provide methods and model organisms to study them, and raise many exciting hypotheses for future work.

Heterotrophic bacterioplankton dynamics have seldom been assessed in the Red Sea, an exceptionally warm oligotrophic basin, which could be used as a model for the future ocean. To understand the function of heterotrophic bacteria in biogeochemical cycles and the flows of matter and energy to higher trophic levels, it is peremptory to understand how bacterial growth is controlled. Bottom-up (resources availability), top-down (mortality by predators and viruses) and temperature are the main hypotheses of control of bacterial activity and stocks. This dissertation aims to assess the spatial-temporal variability of heterotrophic bacteria and their interactions with diverse sources of dissolved organic matter (DOM) through the observed effects on bacterial growth rates and productivity in coastal environments of the central Red Sea. To that end we conducted a total of 66 shortterm incubations (4-6 days) concurrently with the whole microbial community and predator-free (by filtration) in various shallow ecosystems characterized by different dominant sources of DOM. Frequent sampling combined flow cytometry and biogeochemical analysis allowed us to measure bacterial standing stocks, including the carrying capacity (maximum abundances), growth rates, characterize DOM concentrations and lability, assess bacterial DOM consumption rates and biomass production and ultimately quantify bacterial growth efficiencies. Our findings suggest that although bacteria seemed to thrive in nutrient-sufficient waters, the central coastal Red Sea is characterized by unusually low bacterial standing stocks (4.05 ± 0.31 x105 cells ml-1), probably controlled by protistan grazing. At the same time, bacterioplankton showed high potential to grow (0.35-1.75 d-1, reaching 4.16 d-1 when dilution and pre-filtration were performed). Even though the highest specific growth rates were observed during the warmer periods, we did not find any consistent relationship with temperature. While temperature seemed not to constrain bacterial specific growth rates, we observed a tight link between bacterial growth and resource availability in terms of both quantity and quality. Overall, by surveying one of the warmest marine regions on Earth, this dissertation provides detailed insights into heterotrophic bacterioplankton dynamics and how bottomup, top-down and temperature regulate them in tropical waters, a vast geographical extension of the world oceans that had remained strongly undersampled to date.

The objectives of this study were to determine: (1) whether or not heterotrophic microorganisms exert an effect on the trihalomethane (THM) or total organic halogen (TOX) formation potentials of algal extracellular products (ECP), and (2) whether or not diurnal cycling of THM and TOX precursors occurs in vitro. These objectives were addressed through culture studies of heterotrophic microorganisms and pure algae from both the green and blue-green divisions. Culture conditions were varied to study different aspects of algal and bacterial interactions. Results from continuous light assays indicated that heterotrophs, grown in the same culture vessel with algae, affected an increase in the potential of chlorinated culture filtrate to form THMs. No significant changes in TOX-formation potential were observed. Heterotrophs grown in volumes of algal ECP (cell-free filtrates of algal cultures) used the algal-produced organic carbon as their sole carbon source. These microorganisms further reduced both the dissolved organic carbon (DOC) concentration and the concentration of the DOC fraction that reacted to form TOXs. The fraction which produced THMs was not reduced. Heterotrophic microorganism metabolic activity increased the rate at which THMs fanned from chlorinated algal ECP but did not alter the seven-day THM-formation potentials. Their activity also increased the initial rate of TOX formation, but decreased the seven-day formation potential of these compounds. Attempts to demonstrate diurnal cycling of the concentration of THM precursors and other halogenated organic precursors, a phenomenon previously demonstrated in a eutrophic reservoir, were unsuccessful. / M.S.

In aquatic environments the availability of nitrogen (N) generally limits primary production. N2-fixing prokaryotes (diazotrophs) can convert N2 gas into ammonium and provide significant input of N into the oceans. Cyanobacteria are thought to be the main N2-fixers but diazotrophs also include a wide range of heterotrophic bacteria. However, their activity and regulation in the water column is largely unknown. In this thesis the distribution, diversity, abundance, and activity of marine and estuarine heterotrophic diazotrophs was investigated. With molecular methods targeting the nifH gene, encoding the nitrogenase enzyme for N2 fixation, it was shown that diverse nifH genes affiliating with heterotrophic bacteria were ubiquitous in surface waters from ten marine locations world-wide and the estuarine Baltic Sea. Through enrichment cultures of Baltic Sea surface water in anaerobic N-free medium, heterotrophic N2 fixation was induced showing that there was a functional N2-fixing community present and isolates of heterotrophic diazotrophs were obtained. In Sargasso Sea surface waters, transcripts of nifH related to heterotrophic bacteria were detected indicating heterotrophic N2-fixing activity. Nitrogenase expression is thought to be highly regulated by the availability of inorganic N and the presence of oxygen. Low oxygen zones within the water column can be found in association with plankton. The presence of diazotrophs as symbionts of heterotrophic dinoflagellates was investigated and nifH genes related to heterotrophic diazotrophs rather than the cyanobacterial symbionts were found, suggesting that a symbiotic co-existence prevailed. Oxic-anoxic interfaces could also be potential sites for heterotrophic N2 fixation. The Baltic Sea contains large areas of anoxic bottom water. At the chemocline and in anoxic deep water heterotrophic diazotrophs were diverse, abundant and active. These findings extend the currently known regime of N2 fixation to also include ammonium-rich anaerobic waters. The results of this thesis suggest that heterotrophic diazotrophs are diverse and widely distributed in marine and estuarine waters and that they can also be active. However, limits in the knowledge on their physiology and factors which regulate their N2 fixation activity currently prevent an evaluation of their importance in the global marine N budget.