Bacterial Diversity and Sulfur Cycling in a Mesophilic Sulfide-Rich Spring

Abstract

An artesian sulfide-and sulfur-rich spring in southwestern Oklahoma is shown to sustain an extremely rich and diverse microbial community. Laboratory incubations and autoradiography studies indicated that active sulfur cycling is occurring in the abundant microbial mats at Zodletone spring. Anoxygenic phototrophic bacteria oxidize sulfide to sulfate, which is reduced by sulfate-reducing bacterial populations. The microbial community at Zodletone spring was analyzed by cloning and sequencing 16S rRNA genes. A large fraction (83%) of the microbial mat clones belong to sulfur-and sulfate-reducing lineages within ␦-Proteobacteria, purple sulfur ␥-Proteobacteria, -Proteobacteria, Chloroflexi, and filamentous Cyanobacteria of the order Oscillatoria as well as a novel group within ␥-Proteobacteria. The 16S clone library constructed from hydrocarbon-exposed sediments at the source of the spring had a higher diversity than the mat clone library (Shannon-Weiner index of 3.84 compared to 2.95 for the mat), with a higher percentage of clones belonging to nonphototrophic lineages (e.g., Cytophaga, Spirochaetes, Planctomycetes, Firmicutes, and Verrucomicrobiae). Many of these clones were closely related to clones retrieved from hydrocarbon-contaminated environments and anaerobic hydrocarbondegrading enrichments. In addition, 18 of the source clones did not cluster with any of the previously described microbial divisions. These 18 clones, together with previously published or database-deposited related sequences retrieved from a wide variety of environments, could be clustered into at least four novel candidate divisions. The sulfate-reducing community at Zodletone spring was characterized by cloning and sequencing a 1.9-kb fragment of the dissimilatory sulfite reductase (DSR) gene. DSR clones belonged to the DesulfococcusDesulfosarcina-Desulfonema group, Desulfobacter group, and Desulfovibrio group as well as to a deeply branched group in the DSR tree with no representatives from cultures. Overall, this work expands the division-level diversity of the bacterial domain and highlights the complexity of microbial communities involved in sulfur cycling in mesophilic microbial mats.Within sulfur-and sulfide-rich environments (e.g., springs, hydrothermal vents, anaerobic zones of lakes, and shallow marine and intertidal systems), utilization and cycling of sulfur species play a major role in energy production and the maintenance of the microbial community (16). Since a wide array of microorganisms are able to oxidize, reduce, and disproportionate sulfur species, the microbial community structure of sulfurrich habitats is clearly influenced by the prevalent environmental conditions at a specific site, e.g., pH; temperature; sulfide, sulfur, or sulfate concentrations; redox conditions; presence of other electron acceptors; light availability; and organic content.The microbial community structure has been extensively studied in several sulfur-rich habitats, e.g., in hypersaline lakes in Sinai, Egypt (34,46,68,69), and Guerrero Negro, ...

Niche differentiation among sulfur-oxidizing bacterial populations in cave waters

“…Circumstantial evidence suggests that members of this novel clade are sulfur oxidizers (Elshahed et al, 2003;Ito et al, 2005). This study is the first to our knowledge to retrieve a significant percentage of Arcobacter clones from a freshwater environment.…”

Archaea of the Miscellaneous Crenarchaeotal Group are abundant, diverse and widespread in marine sediments

“…MCG are present in terrestrial hot springs , deep oceanic subsurface sediments (Parkes et al, 2005), deep terrestrial subsurface (Inagaki et al, 2003), continental shelf sediments (Vetriani et al, 1998), ancient marine sapropels (Coolen et al, 2002), petroleum-contaminated soil (Kasai et al, 2005), termite guts (Friedrich et al, 2001), mud volcanoes (Heijs et al, 2007), methane hydrate-containing marine sediments (Inagaki et al, 2006), landfill leachate (Huang et al, 2003), anaerobic wastewater reactors (Collins et al, 2005), sulfidic springs (Elshahed et al, 2003), brackish lakes (Hershberger et al, 1996) and coastal salt marshes (Castro et al, 2004). Only 28 out of 4720 MCG sequences were retrieved from potentially oxic habitats (for example, database releases EU370096 and FJ560325).…”

Abundance and diversity of sulphate-reducing bacterioplankton in Lake Suigetsu, a meromictic lake in Fukui, Japan

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