Chemolithotrohic Bacteria: Distributions, Functions and Significance in Volcanic Environments

Abstract

A mosaic of environments comprises most volcanic ecosystems. Whether terrestrial or submarine, many of these environments contain large deposits of reduced minerals, or experience large fluxes of reduced substrates, especially sulfur-containing compounds. These systems, which also are typically characterized by temperature and pH extremes, have yielded a rich variety of chemolithotrophic bacteria, and contributed much to our understanding of chemolithotroph ecology and physiology. However, volcanic ecosystems also consist of environments where inorganic and organic substrates are limiting. In these cases, chemolithotrophs may still play important roles by scavenging carbon monoxide, hydrogen or both. These gases can support metabolism of facultative chemolithotrophs, a functional group that includes many nitrogen-fixing bacteria. Facultative chemolithotrophs may not only represent important early colonists on fresh volcanic substrates (e.g., basalts lacking sulfides), they may also contribute significantly to ecosystem succession through nitrogen fixation and interactions with vascular plants. Analyses of CO and hydrogen consumption by recent deposits on Kilauea volcano show that both substrates support significant activity, while molecular approaches show a high diversity of lithotrophs. Collectively, these and other observations indicate that chemolithotrophic metabolism is more widespread than generally acknowledged, and likely to play fundamental roles in shaping ecosystem dynamics.

Genomic comparison of Bradyrhizobium japonicum strains with different symbiotic nitrogen-fixing capabilities and other Bradyrhizobiaceae members

“…Members of Bradyrhizobiaceae include a number of nonsymbiotic bacteria with diverse biochemical functions such as photosynthesis (Molouba et al, 1999;Larimer et al, 2004;Giraud et al, 2007), oligotrophy (Saito et al, 1998;King, 2007), 2,4-dichlorophenoxyacetic acid degradation (Kamagata et al, 1997) and nitrification (Starkenburg et al, 2006).…”

Thiosulfate-Dependent Chemolithoautotrophic Growth of Bradyrhizobium japonicum

“…Biological oxidation of reduced inorganic sulfur compounds is one of the major reactions in the global sulfur cycle (9,26) and is the major reaction under extreme conditions such as those in deep-sea hydrothermal vents (31), solfataras (23), and volcanic environments (22). The oxidation reactions in these ecosystems are carried out by prokaryotes of the domains Archaea and Bacteria (9,23).…”

Atmospheric CO and Hydrogen Uptake and CO Oxidizer Phylogeny for Miyake-jima, Japan Volcanic Deposits

“…King and collaborators have used both molecular and activity-based approaches to explore relationships between microbial communities and succession on chronosequences of Hawaiian volcanic deposits 7,8,16,18,21,27) . Analyses based on 16S rRNA gene sequences reveal statistically distinct communities on deposits with different ages and different levels of plant development 8) .…”