The Role of The Bacterial Community in the Radionuclide Transfers in Freshwater Ecosystems.

Despite their crucial role in the nitrogen cycle, freshwater ecosystems are relatively rarely studied for active ammonia oxidizers (AO). This study of Lake Lucerne determined the abundance of bothamoAgenes and gene transcripts of ammonia-oxidizing archaea (AOA) and bacteria (AOB) over a period of 16 months, shedding more light on the role of both AO in a deep, alpine lake environment. At the surface, at 42 m water depth, and in the water layer immediately above the sediment, AOA generally outnumbered AOB. However, in the surface water during summer stratification, when both AO were low in abundance, AOB were more numerous than AOA. Temporal distribution patterns of AOA and AOB were comparable. Higher abundances ofamoAgene transcripts were observed at the onset and end of summer stratification. In summer, archaealamoAgenes and transcripts correlated negatively with temperature and conductivity. Concentrations of ammonium and oxygen did not vary enough to explain theamoAgene and transcript dynamics. The observed herbivorous zooplankton may have caused a hidden flux of mineralized ammonium and a change in abundance of genes and transcripts. At the surface, AO might have been repressed during summer stratification due to nutrient limitation caused by active phytoplankton.

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Protozoa abundance, growth, and bacterivory in the water column, on sedimenting particles, and in the sediment of Halifax Harbor

Canadian Journal of Microbiology ◽

10.1139/m90-149 ◽

1990 ◽

Vol 36 (12) ◽

pp. 859-863 ◽

Cited By ~ 6

Author(s):

James A. Novitsky

Keyword(s):

Bacterial Community ◽

Water Column ◽

Sediment Surface ◽

Metabolic Inhibitor ◽

Optimum Conditions ◽

Bacterial Populations ◽

Protozoan Grazing ◽

Large Numbers ◽

Doubling Times

The role of protozoan grazing in controlling bacterial populations was examined in four microbial habitats in Halifax Harbor, Canada: the water column, setting particles, the sediment–water interface, and the sediment. Large numbers of protozoans were found in all habitats although most (>56%) were small (<5 μm) flagellates. Protozoans larger than 10 μm were rarely observed; protozoans >20 μm were never observed. Protozoans were also observed to a depth of 9 cm below the sediment surface although efforts to culture viable protozoa failed except for the top 1 cm. The use of the metabolic inhibitor cycloheximide with and without colchicine to selectively inhibit eucaryotic metabolism was shown to severely affect procaryotic metabolism in sediment (and presumably particle and water) samples. Using fluorescently labelled bacteria as food, and under optimum conditions, up to 42% of the Protozoa population exhibited active grazing within 7 h. Using protozoan and bacterial community sizes and doubling times, it was calculated that each protozoan in Halifax Harbor would have to consume 13–118 bacteria per hour for the enumerated nanoplanktonic (<20 μm) Protozoa to be the sole control of the size of the bacterial community. Key words: marine, Protozoa, bacterivory, particles, bacteria.

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Phylogenetic and Functional Diversity of Saprolegniales and Fungi Isolated from Temperate Lakes in Northeast Germany

Journal of Fungi ◽

10.3390/jof7110968 ◽

2021 ◽

Vol 7 (11) ◽

pp. 968

Author(s):

Hossein Masigol ◽

Jason Nicholas Woodhouse ◽

Pieter van West ◽

Reza Mostowfizadeh-Ghalamfarsa ◽

Keilor Rojas-Jimenez ◽

...

Keyword(s):

Organic Matter ◽

Dissolved Organic Matter ◽

Enzymatic Activity ◽

Humic Substances ◽

Plant Litter ◽

Freshwater Ecosystems ◽

Chitinolytic Activity ◽

Ecological Implications ◽

Eukaryotic Organisms

The contribution of fungi to the degradation of plant litter and transformation of dissolved organic matter (humic substances, in particular) in freshwater ecosystems has received increasing attention recently. However, the role of Saprolegniales as one of the most common eukaryotic organisms is rarely studied. In this study, we isolated and phylogenetically placed 51 fungal and 62 Saprolegniales strains from 12 German lakes. We studied the cellulo-, lignino-, and chitinolytic activity of the strains using plate assays. Furthermore, we determined the capacity of 10 selected strains to utilize 95 different labile compounds, using Biolog FF MicroPlates™. Finally, the ability of three selected strains to utilize maltose and degrade/produce humic substances was measured. Cladosporium and Penicillium were amongst the most prevalent fungal strains, while Saprolegnia, Achlya, and Leptolegnia were the most frequent Saprolegniales strains. Although the isolated strains assigned to genera were phylogenetically similar, their enzymatic activity and physiological profiling were quite diverse. Our results indicate that Saprolegniales, in contrast to fungi, lack ligninolytic activity and are not involved in the production/transformation of humic substances. We hypothesize that Saprolegniales and fungi might have complementary roles in interacting with dissolved organic matter, which has ecological implications for carbon cycling in freshwater ecosystems.

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Role of C-Reactive Protein and Procalcitonin in Differentiation of Tuberculosis from Bacterial Community Acquired Pneumonia

The Korean Journal of Internal Medicine ◽

10.3904/kjim.2009.24.4.337 ◽

2009 ◽

Vol 24 (4) ◽

pp. 337 ◽

Cited By ~ 25

Author(s):

Young Ae Kang ◽

Sung-Youn Kwon ◽

Ho IL Yoon ◽

Jae Ho Lee ◽

Choon-Taek Lee

Keyword(s):

Bacterial Community ◽

Community Acquired Pneumonia ◽

C Reactive Protein ◽

Reactive Protein

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Freshwater Perkinsea: diversity, ecology and genomic information

Journal of Plankton Research ◽

10.1093/plankt/fbz068 ◽

2019 ◽

Vol 42 (1) ◽

pp. 3-17 ◽

Cited By ~ 2

Author(s):

M Jobard ◽

I Wawrzyniak ◽

G Bronner ◽

D Marie ◽

A Vellet ◽

...

Keyword(s):

Phylogenetic Analyses ◽

Meta Analysis ◽

Freshwater Ecosystems ◽

Protein Coding ◽

Lake Ecosystems ◽

Operational Taxonomic Units ◽

Clade 1 ◽

Almost All ◽

Parasitic Association

Abstract Studies on freshwater Perkinsea are scarce compared to their marine counterparts; they are therefore not well ecologically characterized. In this study, we investigated the diversity, distribution and ecological role of Perkinsea in freshwater ecosystems. Our approach included (1) the phylogenetic analyses of near full-length SSU and LSU sequences of freshwater Perkinsea, (2) a meta-analysis of public Perkinsea 18S ribosomal RNA gene sequences available from the freshwater environments (25 lakes, 4 rivers), (3) microscopic observations of Perkinsea associated with planktonic communities and (4) single amplified genome analysis. Whereas Perkinsea appear to be rare in river ecosystems (85 reads), they are found in almost all of the lakes studied. However, their diversity does vary considerably between lakes (from 0 to 2 463 Operational Taxonomic Units (OTUs)). Phylogenetic analysis showed that the Parvilucifera/Dinovorax/Snorkelia and Perkinsus/Xcellia/Gadixcellia clades resulted from an initial speciation event. This second clade is further split into well-supported, monophyletic groups, including a clade dominated by freshwater representatives, which is further structured into three distinct subclades: freshwater clade 1, freshwater clade 2 and a freshwater and brackish clade. The Perkinsea Single Amplified Genome (SAG) as well as most of the abundant Operational Taxonomic Units (OTUs) fall into freshwater clade 2. The tyramide signal amplification-fluorescent in situ hybridization method showed an internal association between Perkinsea and the colonial phytoplankton Sphaerocystis. The Single Amplified Genome (SAG) annotation contained 698 genes and gene ontology terms could be assigned to 486 protein-coding genes. Although the number of genes appears to be low (10.6% of the entire gene set assessed by BUSCO), the analysis of the proteome revealed some putative secreted virulence factors. This study showed a large distribution of Perkinsea across lake ecosystems and potential parasitic association with phytoplankton. However, further investigations are needed for a better knowledge on the role of these microorganisms in freshwater ecosystems.

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