A Combination of Extreme Environmental Conditions Favor the Prevalence of Endospore-Forming Firmicutes

Abstract

Environmental conditions unsuitable for microbial growth are the rule rather than the exception in most habitats. In response to this, microorganisms have developed various strategies to withstand environmental conditions that limit active growth. Endospore-forming Firmicutes (EFF) deploy a myriad of survival strategies in order to resist adverse conditions. Like many bacterial groups, they can form biofilms and detect nutrient scarcity through chemotaxis. Moreover, within this paraphyletic group of Firmicutes, ecophysiological optima are diverse. Nonetheless, a response to adversity that delimits this group is the formation of wet-heat resistant spores. These strategies are energetically demanding and therefore might affect the biological success of EFF. Therefore, we hypothesize that abundance and diversity of EFF should be maximized in those environments in which the benefits of these survival strategies offsets the energetic cost. In order to address this hypothesis, geothermal and mineral springs and drillings were selected because in these environments of steep physicochemical gradients, diversified survival strategies may become a successful strategy.We collected 71 samples from geothermal and mineral environments characterized by none (null), single or multiple limiting environmental factors (temperature, pH, UV radiation, and specific mineral composition). To measure success, we quantified EFF gene copy numbers (GCN; spo0A gene) in relation to total bacterial GCN (16S rRNA gene), as well as the contribution of EFF to community composition. The quantification showed that relative GCN for EFF reached up to 20% at sites characterized by multiple limiting environmental factors, whereas it corresponded to less than 1% at sites with one or no limiting environmental factor. Pyrosequencing of the 16S rRNA gene supports a higher contribution of EFF at sites with multiple limiting factors. Community composition suggested a combination of phylotypes for which active growth could be expected, and phylotypes that are most likely in the state of endospores, in all the sites. In summary, our results suggest that diversified survival strategies, including sporulation and metabolic adaptations, explain the biological success of EFF in geothermal and natural springs, and that multiple extreme environmental factors favor the prevalence of EFF.

Similar but Not Identical Resuscitation Trajectories of the Soil Microbial Community Based on Either DNA or RNA after Flooding

“…Our results showed that Bacillales, the order within the class Bacilli, overwhelmingly dominated in relative abundance in the intermediate pattern (8-48 h) and were largely responsible for differences in microbial response to flooding, although the detected richness of the community that responded intermediately was less than that of results from the study of Placella et al [6]. The lesser community richness in the intermediate pattern may depend on, not only the different soil with distinct properties and indigenous microorganisms, but also on the eventual water conditions, since abrupt flooding of dry soil in our experiment may delay and impede the growth of taxa which should have grown intermediately under favorable moisture conditions, such as some other species of Firmicutes [59]. This indicates the potential effects of Bacilli, the intermediate responder, on ultimate microbial ecology and soil ecosystem functioning due to their particular ecological function such as the production of hydrolytic enzymes breaking intermediate-sized polymers into monomers [6].…”

“…However, most Actinobacteria were found belonging to the delayed pattern in the total (DNA-based) community, which was possibly explained by a competitive disadvantage during the early hours of rewetting [10]. Secondly, intermediate responders, both in the total and the potentially active community, were generally Firmicutes, a phylum well known for their ability to produce a highly resistant endospores produced in stressful environment [59]. When transferred to favorable conditions such as rewetting from drought, spores could synthesize RNA quickly to recover and grow, then increase in relative abundance.…”

Active microbiome structure and its association with environmental factors and viruses at different aquatic sites of a high‐altitude wetland

“…High-altitude wetland microbial communities have been considered as a hotspot of microbial life (Albarracín et al, 2015;Dorador et al, 2013); however, scarce information is available concerning the factors potentially driving this diversity. Limiting environmental factors, such as, temperature, pH, and mineral composition could favor the presence of certain groups of microorganisms, such as endospore-forming firmicutes in extreme environments (Filippidou et al, 2016). Moreover, factors like salinity could generate niche partitioning among functional groups (Oren, 2001) and salinity plus nutrients were suggested to limit different biotic components of high altitude aquatic environments such as, lakes and lagoons (Márquez-García et al, 2009).…”

Insights into the Microbiological Safety of Wooden Cutting Boards Used for Meat Processing in Hong Kong’s Wet Markets: A Focus on Food-Contact Surfaces, Cross-Contamination and the Efficacy of Traditional Hygiene Practices

“…In sharp contrast, the apparently unhygienic surface conditions of the wooden cutting boards in wet markets, in combination with Hong Kong's high ambient temperature and high relative humidity conditions, are conducive to pathogenic microbial proliferation on freely displayed meat products [4]. It has been reported that certain bacteria belonging to phylum Firmicutes can survive at low temperature [40,41]. For example, some species belonging to this bacterial group have survival mechanisms to withstand harsh environmental conditions [42], such as by producing endospores at low temperatures, which then remain dormant until conditions become favourable [43,44].…”