Abundance Of Heterotrophic Bacteria Research Articles

Abundance and size structure of planktonic protist communities in a Neotropical floodplain: effects of top-down and bottom-up controls

Abstract: Aim: We aimed to assess the influence of bottom-up and top-down control mechanisms on the abundance and size structure of protist communities (heterotrophic flagellates and ciliates). We formulated the following hypothesis: bottom-up control mechanisms, related to the availability of resources in the environment, are responsible for structuring the abundance of these communities, whereas top-down control mechanisms, related to predation effects, determine the size pattern of these organisms. Methods Samples for planktonic organisms were taken in 20 shallow lakes belonging to the upper Paraná River floodplain. We evaluated linear regression models to select the best model which predicts the patterns observed according to Akaike Information Criterion. Results The best models selected to explain the abundance of heterotrophic flagellates included negative relations with picophytoplankton abundance and positive with rotifers abundance, while for their size structure, negative relationships were found with heterotrophic bacteria, ciliates and rotifers biovolumes. In relation to the ciliates, their abundances were positively related to the rotifers and picophytoplankton abundances and negatively with the heterotrophic bacteria abundance. On the other hand, for the size structure, the best models selected strong negative relations with the microcrustaceans biovolumes, in addition to relations with the different fractions of the phytoplankton. Conclusion For both flagellates and ciliates, their abundance is being mainly regulated by a bottom up control mechanism, whereas for the size structure the results showed that both food resources and predators were important, indicating that bottom-up and top-down mechanisms act simultaneously in determining the size of these microorganisms.

Influence of Bizerte city wastewater treatment plant (WWTP) on abundance and antibioresistance of culturable heterotrophic and fecal indicator bacteria of Bizerte Lagoon (Tunisia)

The waste water treatment plant (WWTP) of the city of Bizerte concentrates different types of chemical and biological pollutants in the Bizerte lagoon (Tunisia). Considering four upstream and downstream WWTP discharge stations, seventy nine, culturable bacterial strains were isolated and identified from water and sediment as fecal coliforms, fecal streptococci, pathogenic staphylococci and non-enterobacteriacea. Fecal coliforms were most abundant (2.5 105 bacteria/mg) in sediment of WWTP discharge. Leuconostoc spp (23.1%) and Chryseomonasluteola (23.1%) were the most prevalent culturable fecal indicator bacteria (FIB) isolated at the upstream discharge stations. However, Staphylococcus xylosus (13.9%) was the most prevalent culturable FIB isolated at the WWTP discharge stations. Moreover, high antibioticresistance phenotypes were present in all sampling stations, but especially in WWTP discharge station in both water and sediment. Resistance levels in water and sediment, respectively were amoxicillin (58.8%; 34.8%), penicillin (50%; 31.6%), oxacillin (60%; 33.3%), cefotaxim (55.2%; 39.1%), ceftazidim (66.7%; 50%), gentamycin (42.9%; 38.9%), tobramycin (50%; 25%), vancomycin (33.3; 71.4%), amikacin (66.7%; 0%) and ciprofloxacin (100%; 100%). Interestingly, ß-lactam antibiotic resistant FIB were mostly isolated from water as well as from sediments of upstream and WWTP discharge station. Canonical correspondence analysis CCA correlating antibiotic resistance profile with the abiotic data showed that, in water column, culturable bacterial strains isolated in upstream WWTP discharge stations were interestingly correlated with the resistance to amikacin, oxacillin, cefotaxim, ciprofloxacin and gentamycin, however, in sediment, they were correlated with the resistance to amoxicillin, oxacillin, céfotaxim and vancomycin. Serious ß-lactams and aminoglycosides acquired resistance appeared mainly in fecal streptococci and pathogen staphylococci groups.

Application of enzyme-hydrolyzed cassava dregs as a carbon source in aquaculture

As a kind of tropical agricultural solid waste, cassava dregs had become a thorny nonpoint source pollution problem. This study investigated the feasibility of applying cassava dregs as a substitute for sucrose in biofloc technology (BFT) systems. Three types of biofloc systems (using three different carbon sources sucrose (BFT1), cassava dregs (BFT2) and enzyme-hydrolyzed cassava dregs (BFT3) respectively), and the control were constructed in this experiment in 200L tanks with a C/N ratio of 20/1. The comparison of the water quality indicators (The total ammonia nitrogen (TAN), nitrite (NO2−-N), nitrate (NO3−-N), chemical oxygen demand (COD)), biofloc for the above four groups was performed, and the results indicated that BFT3 showed greater potential to the formation of biofloc, which was beneficial for the water quality control. So the shrimp survival rate was the highest and the feed conversion rate was the lowest in BFT3. Besides, the high-throughput sequencing results showed that the relative abundance of heterotrophic bacteria in the top 30 dominant microbial communities in BFT3 was higher than those in BFT1 and BFT2 by 20.70% and 1.19%, respectively, which could decrease TAN to improve the water quality. Overall, the results had proved that the cassava dregs of enzymes hydrolysis could be used as an ideal and cheap carbon source in BFT.

Subsurface low dissolved oxygen occurred at fresh- and saline-water intersection of the Pearl River estuary during the summer period

Estuarine oxygen depletion is one of the worldwide problems, which is caused by the freshwater-input-derived severe stratification and high nutrients loading. In this study we presented the horizontal and vertical distributions of dissolved oxygen (DO) in the Pearl River estuary, together with temperature, salinity, chlorophyll a concentration and heterotrophic bacteria abundance obtained from two cruises during the summer (wet) and winter (dry) periods of 2015. In surface water, the DO level in the summer period was lower and varied greater, as compared to the winter period. The DO remained unsaturated in the summer period if salinity is <12 and saturated if salinity is >12; while in the winter period it remained saturated throughout the estuary. In subsurface (>5m) water, the DO level varied from 0.71 to 6.65mgL−1 and from 6.58 to 8.20mgL−1 in the summer and winter periods, respectively. Particularly, we observed an area of ~1500km2 low DO zone in the subsurface water with a threshold of 4mgDOL−1 during this summer period, that located at the fresh- and saline-water intersection where is characterized with severe stratification and high heterotrophic bacteria abundance. In addition, our results indicate that spatial DO variability in surface water was contributed differently by biological and physio-chemical variables in the summer and winter periods, respectively.

Abundance, biomass, and production of heterotrophic bacteria in a large plain reservoir during the ice-covered period

The abundance, biomass, production, and size and morphological structure of heterotrophic bacteria have been determined and their contribution to the total plankton biomass has been assessed in the Rybinsk Reservoir (the Upper Volga) during the ice-covered period. Structural and functional characteristics of bacteria, except for their cell sizes in winter, are lower than those in the growing season. However, heterotrophic bacteria have made the main contribution (89.3%) to the total biomass of plankton community in winter. During the growing season, phytoplankton is a major component of plankton (48.8%), while the bacteria average 36.5%. The total plankton biomass under the ice averages 148 mg C/m3, which is 2.6 times lower than in the period of open water. During the ice-covered period, the number of protists is small and they consume an insignificant part of the bacterial production; viral lysis is the main reason for bacterial mortality.

Factors influencing the characteristics and distribution or surface organic matter in the Pacific-Atlantic connection

Abstract The present work reports the first data set on particulate organic carbon (POC) and nitrogen (PON), and the high-resolution modelling of their stable isotope variability in the Patagonian Cold Estuarine System (PCES), with focus on particulate organic matter (POM) origin and distribution in dependence on physical, chemical and biological parameters. POC, PON, stable carbon (δ13C) and nitrogen isotopes (δ15N), dissolved organic nitrogen, phaeopigments, diatom, dinoflagellate and heterotrophic bacteria (HB) abundance are reported for 17 stations in different waters masses in the southern end of the Argentine shelf in late summer 2012. Most parameters denote clear differences between Beagle - Magellan Water (BMW), Subantarctic Shelf Water (SSW) and Subantarctic Water (SAW). POC and PON decreased from maxima in BMW to intermediate values in SSW and minima in SAW. There was a highly significant correlation among POC, PON and fluorescence indicators of diagenetic maturity of dissolved humic matter. This, together with the inverse correlations of salinity with POC and PON, and the wide range of C:N ratios indicate that POM in the study area is partly derived from terrestrial runoff, superimposed by autochthonous components from plankton of different life stages. HB abundance was significantly correlated with POC and dissolved organic matter (DOM), likely reflecting a resource control of HB and a significant contribution of bacterial biomass to POM in the nanoparticle fraction. The direct relationship between HB and dissolved humics suggests bacterial uptake of DOM fractions otherwise considered refractory. POM complexity was reflected in a wide variation of δ13C, despite the narrow temperature range of this region. The variability of stable isotopes of POC could be accounted for by a model with a degree of detail hitherto not reported in the literature. A multiple regression including C:N ratio, ammonium and the quotient between log abundance of diatoms, dinoflagellates and HB explained 92% of δ13C variance, mostly produced by ammonium. Despite the strong effect of ammonium on δ13C, δ15N variability was largely explained by a strong inverse relationship with the fraction of unutilized nitrate, suggesting dominance of nitrate uptake. However, the proportion of presumably isotopically heavier ammonium derived from continental runoff in the marine δ15N-POM pool is unknown and requires investigation of the isotopic composition of dissolved inorganic nitrogen in the PCES. The presented new information and its comparison with data from other sectors of the Argentine shelf constitute a contribution to an approach for the understanding of the organic matter dynamics that can be potentially expanded to the entire Southwest Atlantic.

Seasonal dynamics of algal and bacterial communities in Arctic sea ice under variable snow cover

The abundance of diatoms and heterotrophic bacteria in sea ice rapidly increases during the spring. However, the number and activity of these microorganisms vary with changing environmental conditions and potentially the taxonomic composition of the algal community during this time. In this study, we assessed the spring bottom-ice community composition in Dease Strait, Nunavut, and investigated potential controls of chlorophyll a (chl a), particulate organic carbon (POC), cell abundance, and production from early March until early June. We found that using flow cytometry to estimate photosynthetic nanoeukaryote (2–20 μm) abundance gave results very similar to light microscopy counts, except when pennate diatoms with lengths close to 20 μm, the maximum size detected by flow cytometry, were abundant. Using the average abundance of nanoeukaryotes from the two methods, we documented a change in the size of cells comprising the ice algal community over the spring, from largely pico- (<2 μm), to nano- and microeukaryotes (20–200 μm). This shift in ice algal size corresponded to a bloom in diatoms that drove increases in chl a, POC, and primary productivity. Low-salinity surface waters, limited nutrient availability, as well as seasonally intensifying light in the bottom ice appeared to support dominance of the centric diatom Attheya spp. Increases in the number and productivity of heterotrophic bacteria in this study were correlated with the number of photosynthetic picoeukaryote cells, potentially due to their supply of dissolved organic carbon substrate. Our results suggest that future conditions predicted for the Arctic that include low nutrients and greater light transmission to the bottom of sea ice may favor an ice algal community dominated by centric diatoms versus the more characteristic pennate diatom-dominated community.

Effects of organic carbon enrichment on respiration rates, phosphatase activities, and abundance of heterotrophic bacteria and protists in organic-rich Arctic and mineral-rich temperate soil samples

The release of respiratory CO2 from polar tundra soils depends on the interactions between soil organic carbon and microbial communities, a topic of increasing importance due to global climate change. We experimentally amended samples of organic-rich tundra soil and mineral-rich temperate soil with dissolved organic carbon (DOC) and examined the following (at the same temperature): (1) the effects of DOC enrichment on bacterial and eukaryotic microbial biomasses, respiration, and acid phosphatase activities in both soil types, (2) whether relationships between microbial biomass, respiration, and acid phosphatase activities were similar across soil types, and (3) to what extent DOC enrichment altered the microbial food web in both soil types. Both soil types showed immediate, temporary increases in respiration following C enrichment, though the C source (amino acids, citric acid, or glucose) was an important source of variation. Additionally, a consistent relationship between respiration rates and acid phosphatase activities suggested that C and P cycling were linked in similar ways in the two soil types. The relationships of respiration rate and acid phosphatase activity to bacterial biomass were also consistent across soil types, excepting some amended tundra soil samples, perhaps due to greater protist bacterivory in those samples. In the tundra samples only, changes in predator biomass were accompanied by elevation of bacterial biomass-specific respiration rates. Our findings highlight the potential importance of protist bacterivory on microbial processes in tundra soils, but further research is needed to assess whether microbial food webs differ consistently among soils that vary in organic content.

Responses of heterotrophic bacteria abundance and activity to Asian dust enrichment in the low nutrients and low chlorophyll (LNLC) region of the Northwestern Pacific Ocean

Bacteria, as an essential part of microbial food web, play a significant role in the marine ecosystem. Dust deposits into the surface ocean carrying with vital nutrient such as Inorganic nitrogen and phosphorus etc., which has an important influence on the life activities of heterotrophic bacteria. The microcosm experiments with Asian dust deposition was carried out on board in the station K3 (26.18°N, 136.73°E) in April 2015, aiming to estimate the impact of dust deposition on the oligotrophic Northwestern pacific Sea, the main goal of the present paper was to assess how dust deposition events affect the abundance and activity of heterotrophic bacteria in low nutrient and low chlorophyll (LNLC) sea area. Station K3 located in the central northwestern Pacific Ocean, which has the characteristic of low nutrient and low chlorophyll. The study shows that there was an N–P co-limitation in station K3, and the deposition of Asian dust can increase the abundance, and promote the activity of heterotrophic bacteria in the station K3.

Use of municipal solid wastes for chemical and microbiological recovery of soils contaminated with metal(loid)s

Iron-rich water treatment residues (Fe-WTRs) and municipal solid waste compost (MSWC) were added together at two different total rates (i.e. 0.5% Fe-WTRs+0.5% MSWC and 1% Fe-WTRs+1% MSWC) to a degraded sub-alkaline soil (pH 8.0) contaminated with Sb (∼110 mg kg−1 soil), Pb (∼1200 mg kg−1), Cd (∼23 mg kg−1), and Zn (∼5400 mg kg−1). A large number of chemical and biological endpoints were evaluated to assess the efficacy of the treatments after five months of incubation. Both treatments significantly reduced the labile fractions of the metal(loid)s in soil, especially Sb, while increasing the abundance of culturable heterotrophic bacteria, actinomycetes and fungi (i.e. up to 6.3-, 1.6- and 4.1-fold higher than control respectively). Soil enzyme activities, i.e. dehydrogenase, β-glucosidase and urease, were also significantly enhanced in the treated soils (i.e. up to ∼12-, 3- and 2-fold higher than control respectively). The amendment addition affected the structure of the soil microbial community as highlighted by the higher metabolic potential and catabolic versatility of treated soils (Biolog CLPP) and by the significantly higher α-diversity values based on high throughput partial 16S rRNA gene sequencing. Moreover, analysis of the dominant operational taxonomic units (OTUs) showed differences in the microbial communities of untreated and treated soils. Plant growth (Helichrysum italicum) in the treated soils was greatly stimulated while metal(loid)s uptake was significantly reduced. Overall, the results indicated that the applied treatment could be ideal for the chemical and (micro)biological recovery of sub-alkaline soils contaminated with Sb and co-occurring metals, and H. italicum appears to be a promising plant species for aided phytostabilisation of such soils.

ORGANIC MATTER AND NUTRIENT PROFILE OF THE TWO-CURRENT-REGULATED-ZONE IN THE SOUTHWESTERN SUMATRAN WATERS (SSW)

The Indian Ocean is influenced by monsoon systems which alter the ocean’s physical and chemical properties. Specifically, the southwestern Sumatran waters in the eastern Indian Ocean are considered a dual current regulated zone i.e. affected by South Equatorial Counter Current (SECC) and South Java Current (SJC). This area is considered as having an important role in the transfer of organic matter or the biological pump. However, the information about this area is minimal, especially in terms of organic matter and nutrient profile. This study will update the recent information about the area, including the profile of particulate organic matter (POM), macro-nutrients, total suspended solids (TSS), macromolecule-degradingbacteria, and soft bottom macrobenthic organisms sampled from 26 stations in both the SECC-regulated zone and the SJC-regulated zone. The physical profile is typical of tropical watersand both zones have a distinct profile of organic matter and nutrients. The particulate organic carbon (POC), particulate organic nitrogen (PON), and TSS of the SECC-regulated zone can be considered higher than those of the SJC-regulated zone. This region is categorized as mesotrophic waters, especially from the surface up to 100 m. The production of nutrients and organic matter in the water column in this area contribute significantly to the abundance of heterotrophic bacteria and benthic organisms.

Harnessing fertilizer potential of human urine in a mesocosm system: a novel test case for linking the loop between sanitation and aquaculture.

Human urine (HU) is a biogenic fertilizer which has raised immense interest owing to its capacity of combining sanitation and nutrient recovery. In search of an alternative organic fertilizer for fish culture, the nutrient potential of HU was evaluated. Fries of Indian carps and larvae of freshwater prawn were reared for 120days under six conditions: (a) aerated and (b) non-aerated fresh HU (0.01%), (c) cattle manure (CM; 1.8kgtank-1), mixed treatment with CM and HU under (d) iso-phosphorus and (e) iso-nitrogenous condition and (f) control. Monitoring of water quality and biological parameters revealed that total fish yield was the highest in CM (621.5gtank-1) followed by mixed treatments under iso-nitrogenous (428gtank-1) and iso-phosphorus (333gtank-1) conditions, aerated HU (321gtank-1) and HU (319gtank-1). The gross primary productivity (GPP) in HU was satisfactory (601.8mgCm-2h-1) and superior to all but CM treatment. The abundance of heterotrophic bacteria (HB) was highest in CM and lowest in HU. Both GPP and HB population were correlated positively with fish yield per tank. Although pH in all treatments remained high (pH 8.4-8.9), no ammonia toxicity was observed. No E. coli infestation in any fish muscle was encountered. The concentrations of cadmium and lead in fish muscle were within respective safe level. The study established that high fertilizer potential of HU could be exploited as an alternative organic fertilizer or as a candidate to be blended with cattle manure.

Characteristics of picoplankton abundances during a Thalassiosira diporocyclus bloom in the Taiwan Bank in late winter

To understand the variations of picoplankton (Prochlorococcus, Synechococcus, picoeukaryotes, and heterotrophic bacteria) abundances during diatom bloom, the distribution of picoplankton in the Taiwan Bank, South China Sea was investigated using flow cytometry during a Thalassiosira diporocyclus bloom in March 2016. The results indicated an abrupt abundance decrease for Prochlorococcus, Synechococcus, and picoeukaryotes within the bloom area while the abundance of heterotrophic bacteria showed no significant difference between the bloom and non-bloom areas. We found two sub-groups of heterotrophic bacteria: high- and low-nucleic acid content (HNA and LNA) bacteria with HNA dominated in the bloom area whereas LNA dominated in the non-bloom area. Among the picoplankton components, HNA represented the highest (61.1%) carbon biomass in the bloom area while picoeukaryotes represented the highest (37.6%) in the non-bloom area. Our findings implied that heterotrophic bacteria, especially HNA, played an essential role during the diatom bloom.

Bacterial and chemical pollution level of the river Turag, Gazipur, Bangladesh

The river Turag is the upper tributary of the river Buriganga in Bangladesh. Aerobic heterotrophic bacterial count of the river in nutrient agar (NA) and peptone yeast extract glucose (PYG) agar media ranged from 2.91 × 105 to 27.5 × 105 cfu/ml and from 1.09 × 105 to 19.3 × 105 cfu/ml, respectively. Enteric and related bacterial count on MacConkey agar was between 0.88 × 103 and 20.8 × 103 cfu/ml. Out of 91 isolated bacterial isolates, 30 were selected based on their distinctive colony morphology for detailed study. Among these, 16 were Grampositive (53%) and 14 were Gram-negative (47%). Bacillus was dominant among the Gram-positive isolates (69%). The remaining were Brochothrix thermosphacta (6%), Caryophanon sp. (19%) and Renibacterium salmoninarum (6%). Fourteen Gram-negative, enteric and related isolates were identified as Plesiomonas shigelloides (43%), Alcaligenes denitrificans (22%), E. coli (14%), Proteus (14%) and Citrobacter freundii (7%). Biological oxygen demand (BOD) and chemical oxygen demand (COD) values were about 9 and 5-fold higher than standard values whereas dissolved oxygen (DO) of the river was found to be six times less than the standard value. The maximum average TDS, conductivity and turbidity was recorded during the summer season as 441.75 ± 15.52 mg/l, 858.25 ± 19.57 μS/cm and 79.53 ± 6.49 NTU, respectively. Chemical contents viz. sulphate, chloride and fluoride were found to be satisfactory from pollution point of view. Both BOD and COD values along with the abundance of different heterotrophic and enteric bacteria clearly indicated that the river Turag was polluted with organic, chemical and bacterial pollutants.&#x0D; Dhaka Univ. J. Biol. Sci. 26(1): 1-11, 2017 (January)

Abundance, Biomass and Production of Heterotrophic Bacteria in a Large Plain Reservoir During the Ice-Covered Period

Abundance, Biomass and Production of Heterotrophic Bacteria in a Large Plain Reservoir During the Ice-Covered Period

Sediment microbial activity and its relation to environmental variables along the eastern Gulf of Finland coastline

Abstract Sediment microbial activity and its relationship with the main environmental factors and pollutants were examined in the coastal area of the eastern Gulf of Finland, Baltic Sea. The activity of two common oxidoreductase enzymes: dehydrogenase (DA) and catalase (CA) varied significantly between 13 study sites. In the Neva Bay the highest microbial activities (DA: 2.64 mg TFF (10 g − 1 ) day − 1 , CA: 6.29 mg H 2 O 2 g − 1 ) were recorded, while in the outer estuary the minimum values of dehydrogenase and catalase were measured. DA, CA, and abundances of culturable heterotrophic bacteria (CHB) were positively correlated with each other, while biomass of green opportunistic algae was independent of both microbial activities and CHB. Enzymatic activity was found to be strongly positively correlated with sediment particle size and organic matter content, but unrelated to the other studied environmental parameters (temperature, pH, and salinity). Principal components analysis (PCA), controlling for environmental variables, supported direct effects of metal and oil contamination on sediment microbial activity. Also it had shown the similar patterns for algal biomass and metals. Our results suggest that copper and hydrocarbons are the main anthropogenic variables influencing enzyme distribution along the eastern Gulf of Finland coastline.

Pico and nanoplankton abundance and carbon stocks along the Brazilian Bight.

Pico and nanoplankton communities from the Southwest Atlantic Ocean along the Brazilian Bight are poorly described. The hydrography in this region is dominated by a complex system of layered water masses, which includes the warm and oligotrophic Tropical Water (TW), the cold and nutrient rich South Atlantic Central Water (SACW) and the Coastal Water (CW), which have highly variable properties. In order to assess how pico- and nanoplankton communities are distributed in these different water masses, we determined by flow cytometry the abundance of heterotrophic bacteria, Prochlorococcus, Synechococcus and autotrophic pico and nanoeukaryotes along three transects, extending from 23°S to 31°S and 39°W to 49°W. Heterotrophic bacteria (including archaea, maximum of 1.5 × 106 cells mL−1) were most abundant in Coastal and Tropical Water whereas Prochlorococcus was most abundant in open-ocean oligotrophic waters (maximum of 300 × 103 cells mL−1). Synechococcus(up to 81 × 103 cells mL−1), as well as autotrophic pico and nanoeukaryotes seemed to benefit from the influx of nutrient-rich waters near the continental slope. Autotrophic pico and nanoeukaryotes were also abundant in deep chlorophyll maximum (DCM) layers from offshore waters, and their highest abundances were 20 × 103 cells mL−1 and 5 × 103 cells mL−1, respectively. These data are consistent with previous observations in other marine areas where Synechococcus and autotrophic eukaryotes dominate mesotrophic waters, whereas Prochlorococcus dominate in more oligotrophic areas. Regardless of the microbial community structure near the surface, the carbon stock dominance by autotrophic picoeukaryotes near the DCM is possibly linked to vertical mixing of oligotrophic surface waters with the nutrient-rich SACW and their tolerance to lower light levels.

Diversity of retrievable heterotrophic bacteria in Kongsfjorden, an Arctic fjord.

The diversity and abundance of retrievable pelagic heterotrophic bacteria in Kongsfjorden, an Arctic fjord, was studied during the summer of 2011 (June, August, and September). Retrievable bacterial load ranged from 103 to 107 CFU L−1 in June, while it was 104–106 CFU L−1 in August and September. Based on 16S rRNA gene sequence similarities, a higher number of phylotypes was observed during August (22 phylotypes) compared to that during June (6 phylotypes) and September (12 phylotypes). The groups were classified into four phyla: Firmicutes, Actinobacteria, Proteobacteria, and Bacteroidetes. Bacteroidetes was represented only by a single member Leewenhoekiella aequorea during the three months and was dominant (40%) in June. However, this dominance changed in August to a well-known phytopathogenic species Rhodococcus fascians (32%), which could be a result of decrease in the phytoplankton biomass following the secondary bloom. It is the first report of Halomonas titanicae isolation from the Arctic waters. It showed an increase in its abundance with the intrusion of Atlantic water into Kongsfjorden. Increased abundance of Psychrobacter species in the late summer months coincided with the presence of cooler waters. Thus, the composition and function of heterotrophic bacterial community was fundamentally different in different months. This could be linked to the changes in the water masses and/or phytoplankton bloom dynamics occurring in Arctic summer.

The chemicals (formaldehyde and toluene) influence on soil microorganisms of leached chernozem

The paper assesses the status of the soil cover associated with the pollution of its waste chemical production and consumption. The authors present the data of formaldehyde and toluene influence on the abundance of actinomycetes, heterotrophic bacteria and fungi, as these groups of microorganisms provide self-purification capacity of the soil and participate in soil formation processes. In this paper microbiological and physico-chemical methods of research are used. The study of species composition changes of some soil microorganisms groups of leached chernozem under the influence of formaldehyde and toluene showed that this factor causes changes in the complex of soil microorganisms. This factor is reflected in the decreased species richness and diversity and increase of pollution-tolerant microorganisms. These studies investigate a number of microorganisms that provide self-purification capacity of the soil and participate in soil formation. The results show the nature of the influence of different doses of formaldehyde and toluene on the structure and functioning of the complex of soil microorganisms, as well as reveal the mechanism of action of chemicals (formaldehyde and toluene) on soil microbiota associated with its resistance and the manifestation of toxicity of the soil.

Estimating microbial populations by flow cytometry: Comparison between instruments

For almost three decades, flow cytometry has allowed researchers to investigate ocean planktonic communities using size and cell fluorescence properties. However, oceanographic applications must face two constraints. First, when dealing with marine microbes, instruments must be sensitive because these organisms are very small and with low fluorescence. Second, instruments must be portable to be used on board ships. We compared the performance of two instruments, the BD FACSCanto™ and BD Accuri™ C6. The former is an expensive laboratory-based instrument which has a very good sensitivity, whilst the latter is less sensitive but presents critical advantages for field studies (easy handling and transportation, relatively low cost). We have analyzed 102 samples from the South Atlantic Ocean from three transects off Brazil, within the euphotic zone. We compared cell abundance of heterotrophic bacteria, Prochlorococcus and Synechococcus, as well as photosynthetic pico- and nano-eukaryotes. Heterotrophic bacteria, pico- and nano-eukaryotes could be easily detected with both cytometers. Prochlorococcus and Synechococcus populations were severely under-estimated with the BD Accuri™ C6, particularly for samples from the well-lit layers of the water column. Correction of abundance data using previously suggested approaches was not sufficient to fully compensate for the low sensibility. Our data suggest that the BD Accuri™ C6 is suitable for counting marine bacteria and photosynthetic eukaryotes, but not Prochlorococcus and Synechococcus.