![]() ![]() Generalists with multiple physiological capabilities are able to deal with broader redox regimes than specialists focusing on a single metabolism. Īcclimatization can also occur on the community level. ![]() In tropical forest soils, many taxa displayed sustained activity through rapidly fluctuating redox conditions. In intertidal sediments, transcription of genes for aerobic respiration and denitrification was not affected by oxygen concentrations. For example, in bioreactors cycled every 6–12 h, relatively few proteins were found responsive between oxic and anoxic phases. Alternatively, they may constitutively express a multifunctional proteome that provides answers to different conditions. Instead of responding to change, microbes may survive a period of unfavorable conditions without adaptation, counting on conditions to become more favorable quickly enough. Both protein biosynthesis and protein degradation cost energy and consume ATP. After all, regulation is associated with trade-offs, such as the bio-energetic costs associated with accelerated turnover of the proteome. Often, change affects redox conditions and triggers microbial response, which is the topic of this study.Įven though it is often assumed that microbes are always responsive to their environment, this is not necessarily the case. Seasons dictate change in lakes, with water columns mixing in winter and stratifying during summer. Cyanobacteria display a progression of gene expression in response to diurnal cycles. Microbiomes of the oral and digestive-tract of animals experience dynamics associated with feeding regimes, leading to cycles of feast and famine multiple times per day. ![]() Microbes, the smallest and most abundant cellular organisms, are coping with change all the time. “Changes are in diverse forms, up or down, rigid or flexible, and throughout the whole universe”, as stated in I Ching, an ancient Chinese divination text, ~1000 BC. “The only constant in life is change”, according to the philosopher Heraclitus, ~500 BC in Ancient Greece. (3) Alignment of transcriptomes and proteomes required multiple generations and was dependent on a low frequency of change. (2) A high frequency of change selected for strong codon usage bias. Our results supported three conclusions: (1) Oscillating oxic/anoxic conditions selected for generalistic species, rather than species specializing in only a single condition. Almost all these populations maintained a steady growth rate under both redox conditions at all three frequencies of change. Metagenomics resolved provisional genomes of all abundant bacterial populations, mainly affiliated with Proteobacteria and Bacteroidetes. The microbial response was recorded with 16S rRNA gene amplicon sequencing, shotgun metagenomics, transcriptomics and proteomics. The chemostats were submitted to alternatingly oxic and anoxic conditions at three frequencies, with periods of 1, 4 and 16 days. For this, we inoculated replicated chemostats with an enrichment culture obtained from sulfidic stream microbiomes 16 weeks prior. Here, we used controlled laboratory experiments to investigate the effectiveness of different response strategies, such as post-translational modification, transcriptional regulation, and specialized versus adaptable metabolisms. Nature challenges microbes with change at different frequencies and demands an effective response for survival. ![]()
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