Interaction of Nutrient Limitation and Protozoan Grazing Determines the Phenotypic Structure of a Bacterial Community

2003 ◽  
Vol 45 (4) ◽  
pp. 384-398 ◽  
Author(s):  
C. Matz ◽  
K. J�rgens
Keyword(s):  
Bacterial Community ◽  
Nutrient Limitation ◽  
Protozoan Grazing ◽  
Phenotypic Structure

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

1990 ◽  
Vol 36 (12) ◽  
pp. 859-863 ◽  
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.

scholarly journals Seasonal and Successional Influences on Bacterial Community Composition Exceed That of Protozoan Grazing in River Biofilms

2012 ◽  
Vol 78 (6) ◽  
pp. 2013-2024 ◽  
Author(s):  
Jennifer K. Wey ◽  
Klaus Jürgens ◽  
Markus Weitere
Keyword(s):  
Bacterial Community ◽  
Community Composition ◽  
Bacterial Community Composition ◽  
Bacterial Biofilm ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Bacterial Biofilms ◽  
Heterotrophic Flagellates ◽  
Operational Taxonomic Units ◽  
Protozoan Grazing

ABSTRACTThe effects of protozoa (heterotrophic flagellates and ciliates) on the morphology and community composition of bacterial biofilms were tested under natural background conditions by applying size fractionation in a river bypass system. Confocal laser scanning microscopy (CLSM) was used to monitor the morphological structure of the biofilm, and fingerprinting methods (single-stranded conformation polymorphism [SSCP] and denaturing gradient gel electrophoresis [DGGE]) were utilized to assess changes in bacterial community composition. Season and internal population dynamics had a greater influence on the bacterial biofilm than the presence of protozoa. Within this general framework, bacterial area coverage and microcolony abundance were nevertheless enhanced by the presence of ciliates (but not by the presence of flagellates). We also found that the richness of bacterial operational taxonomic units was much higher in planktonic founder communities than in the ones establishing the biofilm. Within the first 2 h of colonization of an empty substrate by bacteria, the presence of flagellates additionally altered their biofilm community composition. As the biofilms matured, the number of bacterial operational taxonomic units increased when flagellates were present in high abundances. The additional presence of ciliates tended to at first reduce (days 2 to 7) and later increase (days 14 to 29) bacterial operational taxonomic unit richness. Altogether, the response of the bacterial community to protozoan grazing pressure was small compared to that reported in planktonic studies, but our findings contradict the assumption of a general grazing resistance of bacterial biofilms toward protozoa.

scholarly journals Impact of Protozoan Grazing on Bacterial Community Structure in Soil Microcosms

2002 ◽  
Vol 68 (12) ◽  
pp. 6094-6105 ◽  
Author(s):  
Regin Rønn ◽  
Allison E. McCaig ◽  
Bryan S. Griffiths ◽  
James I. Prosser
Keyword(s):  
Community Structure ◽  
Bacterial Community ◽  
Nutrient Solution ◽  
Bacterial Communities ◽  
Bacterial Community Structure ◽  
Denaturing Gradient Gel Electrophoresis ◽  
Rrna Gene ◽  
Soil Microcosms ◽  
Protozoan Grazing ◽  
Protozoan Community

ABSTRACT The influence of grazing by a mixed assemblage of soil protozoa (seven flagellates and one amoeba) on bacterial community structure was studied in soil microcosms amended with a particulate resource (sterile wheat roots) or a soluble resource (a solution of various organic compounds). Sterilized soil was reinoculated with mixed soil bacteria (obtained by filtering and dilution) or with bacteria and protozoa. Denaturing gradient gel electrophoresis (DGGE) of PCR amplifications of 16S rRNA gene fragments, as well as community level physiological profiling (Biolog plates), suggested that the mixed protozoan community had significant effects on the bacterial community structure. Excising and sequencing of bands from the DGGE gels indicated that high-G+C gram-positive bacteria closely related to Arthrobacter spp. were favored by grazing, whereas the excised bands that decreased in intensity were related to gram-negative bacteria. The percentages of intensity found in bands related to high G+C gram positives increased from 4.5 and 12.6% in the ungrazed microcosms amended with roots and nutrient solution, respectively, to 19.3 and 32.9% in the grazed microcosms. Protozoa reduced the average bacterial cell size in microcosms amended with nutrient solution but not in the treatment amended with roots. Hence, size-selective feeding may explain some but not all of the changes in bacterial community structure. Five different protozoan isolates (Acanthamoeba sp., two species of Cercomonas, Thaumatomonas sp., and Spumella sp.) had different effects on the bacterial communities. This suggests that the composition of protozoan communities is important for the effect of protozoan grazing on bacterial communities.

scholarly journals Morphological and Compositional Changes in a Planktonic Bacterial Community in Response to Enhanced Protozoan Grazing

1999 ◽  
Vol 65 (3) ◽  
pp. 1241-1250 ◽  
Author(s):  
Klaus Jürgens ◽  
Jakob Pernthaler ◽  
Sven Schalla ◽  
Rudolf Amann
Keyword(s):  
Bacterial Community ◽  
Bacterial Community Composition ◽  
Heterotrophic Nanoflagellates ◽  
Filamentous Bacteria ◽  
Dominant Group ◽  
Microbial Succession ◽  
Phylogenetic Groups ◽  
Bacterial Assemblage ◽  
Protozoan Grazing ◽  
Freshwater Pond

ABSTRACT We analyzed changes in bacterioplankton morphology and composition during enhanced protozoan grazing by image analysis and fluorescent in situ hybridization with group-specific rRNA-targeted oligonucleotide probes. Enclosure experiments were conducted in a small, fishless freshwater pond which was dominated by the cladoceran Daphnia magna. The removal of metazooplankton enhanced protozoan grazing pressure and triggered a microbial succession from fast-growing small bacteria to larger grazing-resistant morphotypes. These were mainly different types of filamentous bacteria which correlated in biomass with the population development of heterotrophic nanoflagellates (HNF). Small bacterial rods and cocci, which showed increased proportion after removal of Daphnia and doubling times of 6 to 11 h, belonged nearly exclusively to the beta subdivision of the classProteobacteria and the Cytophaga-Flavobacteriumcluster. The majority of this newly produced bacterial biomass was rapidly consumed by HNF. In contrast, the proportion of bacteria belonging to the gamma and alpha subdivisions of theProteobacteria increased throughout the experiment. The alpha subdivision consisted mainly of rods that were 3 to 6 μm in length, which probably exceeded the size range of bacteria edible by protozoa. Initially, these organisms accounted for less than 1% of total bacteria, but after 72 h they became the predominant group of the bacterial assemblage. Other types of grazing-resistant, filamentous bacteria were also found within the beta subdivision ofProteobacteria and the Cytophaga-Flavobacteriumcluster. We conclude that the predation regimen is a major structuring force for the bacterial community composition in this system. Protozoan grazing resulted in shifts of the morphological as well as the taxonomic composition of the bacterial assemblage. Grazing-resistant filamentous bacteria can develop within different phylogenetic groups of bacteria, and formerly underepresented taxa might become a dominant group when protozoan predation is the major selective pressure.

Phytoextraction of nickel and rhizosphere microbial communities under mono- or multispecies hyperaccumulator plant cover in a serpentine soil

2015 ◽  
Vol 63 (2) ◽  
pp. 92 ◽  
Author(s):  
Marie Rue ◽  
Jessica Vallance ◽  
Guillaume Echevarria ◽  
Patrice Rey ◽  
Emile Benizri
Keyword(s):  
Bacterial Community ◽  
Mixed Culture ◽  
Plant Biomass ◽  
Microbial Biomass Carbon ◽  
Plant Cover ◽  
Translocation Factor ◽  
Ultramafic Soil ◽  
Unplanted Soil ◽  
Phenotypic Structure ◽  
Fungal Genetic

The efficiency of nickel (Ni) phytoextraction by hyperaccumulating Brassicaceae was compared in two types of covers, namely, monoculture or mixed culture. The selected species were from the Pindus Mountains (Greece), including Alyssum murale, Noccaea tymphaea, Leptoplax emarginata and Bornmuellera tymphaea. After 4 months of culture in mesocosms using ultramafic soil (Ni = 1480 mg kg–1), plant biomass yield and Ni concentrations in shoots and roots were recorded for each of six treatments (mixed-culture cover, four monoculture covers and unplanted soil). Microbial biomass carbon, the size of the cultivable rhizosphere bacterial community and its phenotypic structure (Biolog EcoPlates™), bacterial and fungal genetic structure (SSCP), as well as the potential production of auxin compounds, were also evaluated. Moreover, measurements of various microbial enzymes were performed. The biomass and shoot Ni concentration (albeit not significant) of B. tymphaea increased in co-cropping system. A slight acidification of the soil occurred and a strong correlation between pH and the size of the bacterial community was also observed. No significant change in enzyme activity was observed among the cover types, except in the case of arylsulfatase. The phenotypic structure of the bacterial communities and the bacterial and fungal genetic structures appeared to be specific to the type of cover, although the size of the culturable bacterial community did not show variation among treatments. Therefore, on the basis of the bioaccumulation coefficient and the translocation factor, our results showed that B. tympheae, and to a lesser extent N. tympheae, were the two species with the greatest Ni phytoextraction potential in co-culture systems.

Assessment of viral assemblages in different types of wetland water in northeast China using RAPD-PCR

2020 ◽  
Vol 85 ◽  
pp. 183-196
Author(s):  
Y Sun ◽  
J Liu ◽  
Q Yao ◽  
J Jin ◽  
X Liu ◽  
...  
Keyword(s):  
Bacterial Community ◽  
Water Samples ◽  
Northeast China ◽  
Bacterial Community Composition ◽  
Freshwater Wetlands ◽  
Viral Community ◽  
Rapd Pcr ◽  
Wetland Water ◽  
Different Types ◽  
Viral Communities

Viruses are the most abundant and ubiquitous biological entities in various ecosystems, yet few investigations of viral communities in wetlands have been performed. To address this data gap, water samples from 6 wetlands were randomly collected across northeast China; viruses in the water were concentrated by sequential tangential flow filtration, and viral communities were assessed through randomly amplified polymorphic DNA-PCR (RAPD-PCR) with 4 decamer oligonucleotide primers. Principal coordinate analysis and hierarchical clustering analysis of the DNA fingerprints showed that viral community compositions differed among the water samples: communities in the 2 coastal wetlands were more similar to each other than to those in the 4 freshwater wetlands. The Shannon-Weaver index (H) and evenness index (E) of the RAPD-PCR fingerprint also differed among the 6 wetlands. Mantel test revealed that the changes in viral communities in wetland water were most closely related to the water NH4+-N and inorganic C content, followed by total K, P, C and NO3--N. DNA sequence analysis of the excised bands revealed that viruses accounted for ~40% of all sequences. Among the hit viral homologs, the majority belonged to the Microviridae. Moreover, variance partitioning analysis showed that the viral community contributed 24.58% while environmental factors explained 30.56% of the bacterial community variation, indicating that the bacterial community composition was strongly affected by both viral community and water variables. This work provides an initial outline of the viral communities from different types of wetlands in northeast China and improves our understanding of the viral diversity in these ecosystems.

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