Most cited article - PubMed ID 25331011
Seasonal changes of microbial communities in two shallow peat bog lakes
Aerobic anoxygenic phototrophic (AAP) bacteria are an important component of freshwater bacterioplankton. They can support their heterotrophic metabolism with energy from light, enhancing their growth efficiency. Based on results from cultures, it was hypothesized that photoheterotrophy provides an advantage under carbon limitation and facilitates access to recalcitrant or low-energy carbon sources. However, verification of these hypotheses for natural AAP communities has been lacking. Here, we conducted whole community manipulation experiments and compared the growth of AAP bacteria under carbon limited and with recalcitrant or low-energy carbon sources under dark and light (near-infrared light, λ > 800 nm) conditions to elucidate how they profit from photoheterotrophy. We found that AAP bacteria induce photoheterotrophic metabolism under carbon limitation, but they overcompete heterotrophic bacteria when carbon is available. This effect seems to be driven by physiological responses rather than changes at the community level. Interestingly, recalcitrant (lignin) or low-energy (acetate) carbon sources inhibited the growth of AAP bacteria, especially in light. This unexpected observation may have ecosystem-level consequences as lake browning continues. In general, our findings contribute to the understanding of the dynamics of AAP bacteria in pelagic environments.
- Keywords
- acetate, aerobic anoxygenic phototrophic bacteria, carbon limitation, freshwater lakes, lignin, microbial ecology,
- MeSH
- Bacteria, Aerobic metabolism growth & development MeSH
- Bacteria metabolism growth & development genetics MeSH
- Ecosystem MeSH
- Phototrophic Processes * MeSH
- Heterotrophic Processes MeSH
- Lakes microbiology MeSH
- Light MeSH
- Carbon * metabolism MeSH
- Publication type
- Journal Article MeSH
- Names of Substances
- Carbon * MeSH
Aerobic anoxygenic photoheterotrophic (AAP) bacteria represent a functional group of prokaryotic organisms that harvests light energy using bacteriochlorophyll-containing photosynthetic reaction centers. They represent an active and rapidly growing component of freshwater bacterioplankton, with the highest numbers observed usually in summer. Species diversity of freshwater AAP bacteria has been studied before in lakes, but its seasonal dynamics remain unknown. In this report, we analysed temporal changes in the composition of the phototrophic community in an oligo-mesotrophic freshwater lake using amplicon sequencing of the pufM marker gene. The AAP community was dominated by phototrophic Gammaproteobacteria and Alphaproteobacteria, with smaller contribution of phototrophic Chloroflexota and Gemmatimonadota. Phototrophic Eremiobacteriota or members of Myxococcota were not detected. Interestingly, some AAP taxa, such as Limnohabitans, Rhodoferax, Rhodobacterales or Rhizobiales, were permanently present over the sampling period, while others, such as Sphingomonadales, Rhodospirillales or Caulobacterales appeared only transiently. The environmental factors that best explain the seasonal changes in AAP community were temperature, concentrations of oxygen and dissolved organic matter.
Aerobic anoxygenic phototrophic (AAP) bacteria are a common component of freshwater microbial communities. They harvest light energy using bacteriochlorophyll a-containing reaction centers to supplement their predominantly heterotrophic metabolism. We used epifluorescence microscopy, HPLC, and infrared fluorometry to examine the dynamics of AAP bacteria in the mesotrophic lake Vlkov during the seasonal cycle. The mortality of AAP bacteria was estimated from diel changes of bacteriochlorophyll a fluorescence. The AAP abundance correlated with water temperature and DOC concentration. Its maximum was registered during late summer, when AAP bacteria made up 20% of total bacteria. The novel element of this study is the seasonal measurements of AAP mortality rates. The rates ranged between 1.15 and 4.56 per day with the maxima registered in early summer coinciding with the peak of primary production, which documents that AAP bacteria are a highly active component of freshwater microbial loop.
- MeSH
- Bacteria, Aerobic classification genetics isolation & purification radiation effects MeSH
- Biodiversity * MeSH
- Phototrophic Processes MeSH
- Lakes microbiology MeSH
- Oxygen metabolism MeSH
- Seasons MeSH
- Light MeSH
- Publication type
- Journal Article MeSH
- Names of Substances
- Oxygen MeSH
The genus Limnohabitans (Comamonadaceae, Betaproteobacteria) is a common and a highly active component of freshwater bacterioplanktonic communities. To date, the genus has been considered to contain only heterotrophic species. In this study, we detected the photosynthesis genes pufLM and bchY in 28 of 46 strains from three Limnohabitans lineages. The pufM sequences obtained are very closely related to environmental pufM sequences detected in various freshwater habitats, indicating the ubiquity and potential importance of photoheterotrophic Limnohabitans in nature. Additionally, we sequenced and analyzed the genomes of 5 potentially photoheterotrophic Limnohabitans strains, to gain further insights into their phototrophic capacity. The structure of the photosynthesis gene cluster turned out to be highly conserved within the genus Limnohabitans and also among all potentially photosynthetic Betaproteobacteria strains. The expression of photosynthetic complexes was detected in a culture of Limnohabitans planktonicus II-D5T using spectroscopic and pigment analyses. This was further verified by a novel combination of infrared microscopy and fluorescent in situ hybridization.IMPORTANCE The data presented document that the capacity to perform anoxygenic photosynthesis is common among the members of the genus Limnohabitans, indicating that they may have a novel role in freshwater habitats.
- Keywords
- FISH, IR microscopy, Limnohabitans, bacteriochlorophyll, bchY, freshwater Betaproteobacteria, photosynthetic bacteria, pufM,
- MeSH
- Aerobiosis MeSH
- Genes, Bacterial physiology MeSH
- Bacterial Proteins genetics metabolism MeSH
- Comamonadaceae genetics metabolism MeSH
- Photosynthesis genetics MeSH
- Phylogeny MeSH
- Multigene Family physiology MeSH
- Publication type
- Journal Article MeSH
- Names of Substances
- Bacterial Proteins MeSH
Aerobic anoxygenic phototrophs (AAPs) are photoheterotrophic prokaryotes that are widespread in many limnic and marine environments. So far, little is known about their distribution in peat-bog lakes. Seventeen peat-bog lakes were sampled during three summer seasons 2009, 2011, and 2012, and the vertical distribution of AAPs was determined by infrared epifluorescence microscopy. The analysis demonstrated that in the surface layers of the studied lakes, AAP abundance ranged from 0.3 to 12.04 × 10(5) cells mL(-1), which represents <1 to 18.3 % of the total bacteria. The vertical distribution of AAPs confirmed their presence in the upper parts of the water column with minimum numbers in the anoxic bottom waters. We have shown that the AAP abundance was significantly positively correlated with the water pH, and the highest proportion of photoheterotrophs was found in peat-bog lakes with a pH between 6.7 and 7.6. Our results demonstrated an influence of water acidity on the abundance of AAPs, which may reflect a fundamental difference in the microbial composition between acidic and pH neutral peat-bog lakes.
- Keywords
- Aerobic anoxygenic phototrophic bacteria, Environmental factors, Humic and dystrophic lakes, Peat-bog lakes, pH,
- MeSH
- Bacteria, Aerobic physiology MeSH
- Lakes microbiology MeSH
- Oxygen MeSH
- Water Microbiology MeSH
- Wetlands * MeSH
- Environmental Monitoring MeSH
- Soil * MeSH
- Seasons MeSH
- Publication type
- Journal Article MeSH
- Names of Substances
- Oxygen MeSH
- Soil * MeSH
