The passive yet successful way of planktonic life: genomic and experimental analysis of the ecology of a free-living polynucleobacter population
File(s)
Author(s)
Type
Journal Article
Abstract
BACKGROUND: The bacterial taxon Polynucleobacter necessarius subspecies asymbioticus represents a group of planktonic freshwater bacteria with cosmopolitan and ubiquitous distribution in standing freshwater habitats. These bacteria comprise <1% to 70% (on average about 20%) of total bacterioplankton cells in various freshwater habitats. The ubiquity of this taxon was recently explained by intra-taxon ecological diversification, i.e. specialization of lineages to specific environmental conditions; however, details on specific adaptations are not known. Here we investigated by means of genomic and experimental analyses the ecological adaptation of a persistent population dwelling in a small acidic pond. FINDINGS: The investigated population (F10 lineage) contributed on average 11% to total bacterioplankton in the pond during the vegetation periods (ice-free period, usually May to November). Only a low degree of genetic diversification of the population could be revealed. These bacteria are characterized by a small genome size (2.1 Mb), a relatively small number of genes involved in transduction of environmental signals, and the lack of motility and quorum sensing. Experiments indicated that these bacteria live as chemoorganotrophs by mainly utilizing low-molecular-weight substrates derived from photooxidation of humic substances. CONCLUSIONS: Evolutionary genome streamlining resulted in a highly passive lifestyle so far only known among free-living bacteria from pelagic marine taxa dwelling in environmentally stable nutrient-poor off-shore systems. Surprisingly, such a lifestyle is also successful in a highly dynamic and nutrient-richer environment such as the water column of the investigated pond, which was undergoing complete mixis and pronounced stratification in diurnal cycles. Obviously, metabolic and ecological versatility is not a prerequisite for long-lasting establishment of abundant bacterial populations under highly dynamic environmental conditions. Caution should be exercised when generalizing the obtained insights into the ecology and adaptation of the investigated lineage to other Polynucleobacter lineages.
Date Issued
2012-03-20
Date Acceptance
2012-01-30
Citation
PLOS One, 2012, 7 (3)
ISSN
1932-6203
Publisher
Public Library of Science
Journal / Book Title
PLOS One
Volume
7
Issue
3
Copyright Statement
© 2012 Hahn et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Identifier
PII: PONE-D-11-20686
Subjects
Burkholderiaceae
DNA, Bacterial
DNA, Ribosomal
Ecology
Ecosystem
Fresh Water
Genetic Variation
Genome Size
Genomics
Molecular Sequence Data
Oxidative Stress
Phylogeny
Plankton
Sequence Analysis, DNA
General Science & Technology
MD Multidisciplinary
Publication Status
Published
Article Number
e32772