<p>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. </p><p>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) </p><p>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.</p><p>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.</p><p>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.</p>

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, &lt; 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.

Characterizing dissolved organic matter (DOM) composition remains a major unresolved problem in aquatic ecology. "Tryptophan-like" dissolved organic matter fluorescence (FDOM) was found to be a much better predictor of heterotrophic bacterial metabolism in 28 Quebec lakes than dissolved organic carbon (DOC), describing 52, 44, 51 and 55% of the variability in bacterial production (BP), bacterioplankton respiration (BR), total bacterial carbon consumption (TBCC), and total plankton community respiration (CR), respectively. In addition, the study provides indirect support for the view that FDOM represents a product of bacterial activity, rather than a bioavailable substrate. This is the first field study to show that fluorescence spectroscopy can be used to characterize an aspect of DOM composition that is related to bacterial metabolism, and provides results that encourage further exploration of the potential uses of DOM fluorescence spectroscopy as a predictive tool.

The presence of heterotrophic plate count (HPC) bacteria in drinking water distribution systems is usually not considered harmful to the general consumer. However, precautions must be taken regarding the immunocompromised. All water supply authorities in South Africa are lawfully required to provide consumers with high-quality drinking water that complies with South African-and international standards. This study mainly focused on the isolation, identification and characterization of HPC and other bacteria from biofilm-and bulk water samples from two sampling points located within the Potchefstroom drinking water distribution system. Based on five main objectives set out in this study, results indicated that the bulk water at the J.S. van der Merwe building was of ideal quality fit for lifetime consumption. Application of enrichment-and selective media allowed for the isolation of 12 different bacterial morphotypes. These were identified by way of biochemical-and molecular methods as Bacillus cereus, Bacillus subtilis, Brevundimonas spp., Clostridiaceae, Corynebacterium renale, Flavobacteriaceae, Kytococcus sedentarius, Leuconostoc lactic, Lysinibacillus sphaericus, Pseudomonas spp., Staphylococcus aureus and Staphylococcus capitis. The greatest diversity of bacteria was detected early autumn 2008, while the lowest diversity occurred during mid-winter 2007. Bacillus cereus, Kytococcus sedentarius and Staphylococcus capitis displayed potential pathogenic properties on blood agar. Kytococcus sedentarius could be classified as potentially the most pathogenic among the isolates. All isolates displayed multiple-resistant patterns towards tested antibiotics. Corynebacterium renale and Staphylococcus aureus were least resistant bacterial species and Lysinibacillus sphaericus the most resistant. All isolates were susceptible to ciprofloxacin (CIP) and streptomycin (S), but most were resistant to erythromycin (E). Transmission electron microscopy (TEM) allowed for detailed examination of Brevundimonas spp., Pseudomonas spp. and Staphylococcus spp. The capability of Brevundimonas spp. to produce slime and store nutrients within inclusion bodies, suggests the ability of this bacterium to form biofilm and persist in the drinking water for prolonged periods. Despite the inhibitory or toxic effect of copper against bacterial growth, scanning electron microscopy (SEM) revealed the presence of biofilms as well as diatoms on red-copper coupons. Biofilm activity was also observed on reverse-osmosis (RO) filters. Since corrosion was evident on red-copper coupons, it is recommended that prospective studies also look into the significance of microbial induced corrosion (MIC) within the Potchefstroom drinking water distribution system. Other prospects include determining minimum inhibitory concentrations of isolates against antibiotics and the application of culture independent methods such as SSCP and DGGE to investigate biofilm development. The use of diatoms as an index of the drinking water quality is also suggested. / Thesis (M.Sc. (Environmental Science))--North-West University, Potchefstroom Campus, 2010.

The presence of heterotrophic plate count (HPC) bacteria in drinking water distribution systems is usually not considered harmful to the general consumer. However, precautions must be taken regarding the immunocompromised. All water supply authorities in South Africa are lawfully required to provide consumers with high-quality drinking water that complies with South African-and international standards. This study mainly focused on the isolation, identification and characterization of HPC and other bacteria from biofilm-and bulk water samples from two sampling points located within the Potchefstroom drinking water distribution system. Based on five main objectives set out in this study, results indicated that the bulk water at the J.S. van der Merwe building was of ideal quality fit for lifetime consumption. Application of enrichment-and selective media allowed for the isolation of 12 different bacterial morphotypes. These were identified by way of biochemical-and molecular methods as Bacillus cereus, Bacillus subtilis, Brevundimonas spp., Clostridiaceae, Corynebacterium renale, Flavobacteriaceae, Kytococcus sedentarius, Leuconostoc lactic, Lysinibacillus sphaericus, Pseudomonas spp., Staphylococcus aureus and Staphylococcus capitis. The greatest diversity of bacteria was detected early autumn 2008, while the lowest diversity occurred during mid-winter 2007. Bacillus cereus, Kytococcus sedentarius and Staphylococcus capitis displayed potential pathogenic properties on blood agar. Kytococcus sedentarius could be classified as potentially the most pathogenic among the isolates. All isolates displayed multiple-resistant patterns towards tested antibiotics. Corynebacterium renale and Staphylococcus aureus were least resistant bacterial species and Lysinibacillus sphaericus the most resistant. All isolates were susceptible to ciprofloxacin (CIP) and streptomycin (S), but most were resistant to erythromycin (E). Transmission electron microscopy (TEM) allowed for detailed examination of Brevundimonas spp., Pseudomonas spp. and Staphylococcus spp. The capability of Brevundimonas spp. to produce slime and store nutrients within inclusion bodies, suggests the ability of this bacterium to form biofilm and persist in the drinking water for prolonged periods. Despite the inhibitory or toxic effect of copper against bacterial growth, scanning electron microscopy (SEM) revealed the presence of biofilms as well as diatoms on red-copper coupons. Biofilm activity was also observed on reverse-osmosis (RO) filters. Since corrosion was evident on red-copper coupons, it is recommended that prospective studies also look into the significance of microbial induced corrosion (MIC) within the Potchefstroom drinking water distribution system. Other prospects include determining minimum inhibitory concentrations of isolates against antibiotics and the application of culture independent methods such as SSCP and DGGE to investigate biofilm development. The use of diatoms as an index of the drinking water quality is also suggested. / Thesis (M.Sc. (Environmental Science))--North-West University, Potchefstroom Campus, 2010.

Thesis (M.S.)--Mississippi State University. Department of Biological Sciences. / Title from title screen. Includes bibliographical references.

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