Assessing Niche Separation among Coexisting Limnohabitans Strains through Interactions with a Competitor, Viruses, and a Bacterivore

• Published in: Applied and Environmental Microbiology Vol. 76; no. 5; pp. 1406 - 1416
• Main Authors: Šimek, Karel, Kasalický, Vojtěch, Horňák, Karel, Hahn, Martin W, Weinbauer, Markus G
• Format: Journal Article
• Language: English
• Published: Washington, DC American Society for Microbiology 01.03.2010; American Society for Microbiology (ASM)
• Subjects: Bacteria; Bacteriophages - growth & development; Biological and medical sciences; biomass; Coculture Techniques; Comamonadaceae - genetics; Comamonadaceae - growth & development; Comamonadaceae - virology; Cytophagaceae - growth & development; Earth Sciences; Ecosystem; Eukaryota - growth & development; Flectobacillus; Fresh Water - microbiology; Fundamental and applied biological sciences. Psychology; Gene expression; Grazing; Microbial Ecology; Microbiology; Mortality; niches; nucleotide sequences; Oceanography; population dynamics; predators; Ribonucleic acid; ribosomal RNA; RNA; Sciences of the Universe; strain differences; Viruses; Virus; Interaction; Separation
• DOI: 10.1128/AEM.02517-09
• ISSN: 0099-2240; 1098-5336

We investigated potential niche separation in two closely related (99.1% 16S rRNA gene sequence similarity) syntopic bacterial strains affiliated with the R-BT065 cluster, which represents a subgroup of the genus LIMNOHABITANS: The two strains, designated B4 and D5, were isolated concurrently from a freshwater reservoir. Differences between the strains were examined through monitoring interactions with a bacterial competitor, Flectobacillus sp. (FL), and virus- and predator-induced mortality. Batch-type cocultures, designated B4+FL and D5+FL, were initiated with a similar biomass ratio among the strains. The proportion of each cell type present in the cocultures was monitored based on clear differences in cell sizes. Following exponential growth for 28 h, the cocultures were amended by the addition of two different concentrations of live or heat-inactivated viruses concentrated from the reservoir. Half of virus-amended treatments were inoculated immediately with an axenic flagellate predator, Poterioochromonas sp. The presence of the predator, of live viruses, and of competition between the strains significantly affected their population dynamics in the experimentally manipulated treatments. While strains B4 and FL appeared vulnerable to environmental viruses, strain D5 did not. Predator-induced mortality had the greatest impact on FL, followed by that on D5 and then B4. The virus-vulnerable B4 strain had smaller cells and lower biomass yield, but it was less subject to grazing. In contrast, the seemingly virus-resistant D5, with slightly larger grazing-vulnerable cells, was competitive with FL. Overall, our data suggest contrasting ecophysiological capabilities and partial niche separation in two coexisting Limnohabitans strains.