TitleContrasting trends in distribution of four major planktonic betaproteobacterial groups along a pH gradient of epilimnia of 72 freshwater habitats
Publication TypeJournal Article
Year of Publication2012
AuthorsJezbera, J, Jezberova, J, Koll, U, Hornak, K, Šimek, K, Hahn, MW
JournalFEMS Microbiology Ecology
Keywordscompetition, ecological diversification, Limnohabitans, Polynucleobacter

The distribution and abundance of Betaproteobacteria and three of its genera Limnohabitans (R-BT065 lineage), Polynucleobacter (including subclusters Polynucleobacter necessarius and Polynucleobacter acidiphobus/Polynucleobacter difficilis), and Methylophilus across the epilimnia of 72 limnologically diverse freshwater habitats were investigated using fluorescence in situ hybridization. Moreover, seasonal development of Betaproteobacteria subgroups along the longitudinal axis of a reservoir was followed. Betaproteobacteria comprised on average 29.1%, Polynucleobacter 11.6%, P.similar to necessarius 10.1%, P.similar to acidiphobus/difficilis 0.5%, Limnohabitans 8.9%, and Methylophilus 0.9% of total bacterioplankton cells in the investigated habitats. Polynucleobacter necessarius and Limnohabitans coexisted in the majority of habitats but showed contrasting abundance patterns along the pH gradient of habitats (pH, 3.88.5). The observed distribution patterns could theoretically be explained by different preferences for substrate sources, that is, substances of humic origin in acidic waters and algal-derived substances in alkaline waters. However, substrate utilization patterns observed in laboratory experiments indicate no coherent group-specific differences in substrate preferences. Interestingly, similar distribution patterns were revealed for Limnohabitans and P.similar to acidiphobus/difficilis, suggesting similar ecological adaptations of these distantly related taxa. Our findings further emphasize that at least two taxa of freshwater Betaproteobacteria represent ecologically diversified groups. Investigations at higher phylogenetic resolution are required for obtaining further insights into their ecology.