Endospores of thermophilic bacteria as tracers of microbial dispersal by ocean currents

Abstract

Microbial biogeography is influenced by the combined effects of passive dispersal and environmental selection, but the contribution of either factor can be difficult to discern. As thermophilic bacteria cannot grow in the cold seabed, their inactive spores are not subject to environmental selection. We therefore conducted a global experimental survey using thermophilic endospores that are passively deposited by sedimentation to the cold seafloor as tracers to study the effect of dispersal by ocean currents on the biogeography of marine microorganisms. Our analysis of 81 different marine sediments from around the world identified 146 species-level 16S rRNA phylotypes of endospore-forming, thermophilic Firmicutes. Phylotypes showed various patterns of spatial distribution in the world oceans and were dispersal-limited to different degrees. Co-occurrence of several phylotypes in locations separated by great distances (west of Svalbard, the Baltic Sea and the Gulf of California) demonstrated a widespread but not ubiquitous distribution. In contrast, Arctic regions with water masses that are relatively isolated from global ocean circulation (Baffin Bay and east of Svalbard) were characterized by low phylotype richness and different compositions of phylotypes. The observed distribution pattern of thermophilic endospores in marine sediments suggests that the impact of passive dispersal on marine microbial biogeography is controlled by the connectivity of local water masses to ocean circulation.

Estimating the Abundance of Endospores of Sulfate-Reducing Bacteria in Environmental Samples by Inducing Germination and Exponential Growth

“…This is similar to our observations in previous studies on the presence of endospores of thermophilic SRB in sediments from Aarhus Bay, Svalbard (in the Arctic Ocean), and other cold marine sediments (Isaksen et al 1994;Hubert et al 2009;Hubert et al 2010;de Rezende et al 2013;M€ uller et al 2014). Thermophilic Firmicutes were enriched in all previous cases (Isaksen et al 1994;Hubert et al 2009;Hubert et al 2010;M€ uller et al 2014) as well as in the present experiment (de Rezende et al 2013). The exponential increase in SRRs reflects the exponential growth of SRB provided that the amount of sulfate reduced per cell per unit time, i.e.…”

“…One difficulty concerns unambiguously differentiating between active, dormant and dead cells; combinations of methods are required to target these various physiological states (Blagodatskaya and Kuzyakov 2013). It remains however important for many investigations in environmental microbiology to identify and quantify dormant populations in order to understand their role as a seed bank for the persistence of microbial community members in a given environment (Gibbons et al 2013;Yarwood et al 2013) and to understand the mechanisms and the role of dispersal in shaping microbial diversity (Hanson et al 2012;M€ uller et al 2014).…”

Bacteria as Emerging Indicators of Soil Condition

“…A consensus appears to have emerged that environmental factors, rather than dispersal limitations, are dominant drivers of bacterial community composition (5,11). The reduced role of dispersal limitation in determining the beta-diversity of microbial communities, even across broad spatial scales, is presumed to be supported by a global dispersal of microbial cells, including those carried on major atmospheric currents (12) and oceanic currents (13). While there have been numerous bacterial biogeography studies that have employed DNA-fingerprinting techniques over large spatial scales (4,5), DNAsequencing studies at similar scales are comparatively scarce.…”

Deciphering associations between dissolved organic molecules and bacterial communities in a pelagic marine system

“…OTUs only occurring in the DNA-based approach may include rare biosphere taxa that wait for more favorable growth conditions agreeing with their ecological niche (Pedrós-Alió, 2012;Müller et al, 2014) or represent terrestrial or freshwater 'leftovers'. Generally, the number of OTUs recovered in the DNA-based approach is approximately 20% lower compared with the RNA-based approach.…”