Survey of Archaeal Diversity Reveals an Abundance of HalophilicArchaeain a Low-Salt, Sulfide- and Sulfur-Rich Spring

Abstract

The archaeal community in a sulfide-and sulfur-rich spring with a stream water salinity of 0.7 to 1.0% in southwestern Oklahoma was studied by cloning and sequencing of 16S rRNA genes. Two clone libraries were constructed from sediments obtained at the hydrocarbon-exposed source of the spring and the microbial mats underlying the water flowing from the spring source. Analysis of 113 clones from the source library and 65 clones from the mat library revealed that the majority of clones belonged to the kingdom Euryarchaeota, while Crenarchaeota represented less than 10% of clones. Euryarchaeotal clones belonged to the orders Methanomicrobiales, Methanosarcinales, and Halobacteriales, as well as several previously described lineages with no pure-culture representatives. Those within the Halobacteriales represented 36% of the mat library and 4% of the source library. All cultivated members of this order are obligately aerobic halophiles. The majority of halobacterial clones encountered were not affiliated with any of the currently described genera of the family Halobacteriaceae. Measurement of the salinity at various locations at the spring, as well as along vertical gradients, revealed that soils adjacent to spring mats have a much higher salinity (NaCl concentrations as high as 32%) and a lower moisture content than the spring water, presumably due to evaporation. By use of a high-saltplus-antibiotic medium, several halobacterial isolates were obtained from the microbial mats. Analysis of 16S rRNA genes indicated that all the isolates were members of the genus Haloferax. All isolates obtained grew at a wide range of salt concentrations, ranging from 6% to saturation, and all were able to reduce elemental sulfur to sulfide. We reason that the unexpected abundance of halophilic Archaea in such a low-salt, highly reduced environment could be explained by their relatively low salt requirement, which could be satisfied in specific locations of the shallow spring via evaporation, and their ability to grow under the prevalent anaerobic conditions in the spring, utilizing zero-valent sulfur compounds as electron acceptors. This study demonstrates that members of the Halobacteriales are not restricted to their typical high-salt habitats, and we propose a role for the Halobacteriales in sulfur reduction in natural ecosystems.

Elemental sulfur and acetate can support life of a novel strictly anaerobic haloarchaeon

“…Can these organisms use elemental sulfur, which may be very abundant, as the alternative terminal electron acceptor? This question was addressed several times in the past 30 years (Grant and Ross, 1986;Tindall and Trüper, 1986;Elshahed et al, 2004aElshahed et al, , 2004b, but no conclusive answer has been found. Acetate is an abundant electron donor and carbon source in anoxic habitats, which accumulates in the absence of high-potential electron acceptors, such as nitrate or ferric ion (Afshar et al, 1998;Kashevi et al, 2002;Slobodkina et al, 2009).…”

Manantiales salinos: Inventarios de Diversidad Metabólica y filogenética de microorganismos de ambientes salinos

“…Teniendo en cuenta que los microorganismos halófilos de los dominios Archaea y Bacteria tienen un amplio espectro metabólico, se utilizaron diferentes sustratos orgánicos comúnmente reportados como materia orgánica disuelta en sistemas acuáticos proveniente del medio ambiente circundante o de fuentes autóctonas como el fitoplancton, bacteriopláncton y perifiton, ya sea por la producción de exopolisacáridos, la muerte celular o la liberación de exudados (Gremm & Kaplan, 1997). Además, a algunas series se les agregó un suplemento de antibióticos para favorecer el aislamiento de organismos del dominio Archaea como se ha descrito anteriormente (Elshahed, et al, 2004). Después de la esterilización, los MB-AER fueron suplementados con 0,2 g/L de extracto de levadura (Sigma) y con diferentes fuentes de carbono como ácidos orgánicos, alcoholes, azúcares, aminoácidos, polisacáridos y lípidos (Díaz-Cárdenas, 2011).…”

Archaeal Diversity and Their Biotechnological Potential

“…For example, while most halophilic archaea exhibit optimal growth at near neutral pH, many are alkaliphilic and require at least pH 8.5 for growth . Recent molecular studies have revealed the presence of halophilic archaea in several low salinity environments (Elshahed et al, 2004). In addition, Purdy and colleagues (2004) isolated haloarchaea from a coastal salt marsh that exhibited optimal growth at 10% (1.7 M) NaCl but could grow slowly at 2.5% (0.43 M) NaCl.…”

“…The numbers of genera is reached to 35 (November 2011-Euzebylist) and Salarchaeaum is the last added extremely halophilic genus (Shimane et al, 2011). Most species of Halobacteriaceae are true extreme halophiles according to Kushner's definition (Kushner, 1978), however, Halobacteriaceae contains some species which can grow in low salinity for instance, Haloferax sulfurifontis (Elshahed et al, 2004), Haladaptatus paucihalophilus "the spesific epithet refers to low salt loving", (Savage et al, 2007) and Halosarcina pallida (Savage et al, 2008). Diverse 16S rRNA gene sequences related to haloarchaea were recovered from tidal marine and salt marsh sediments, suggesting the existence of haloarchaea capable of growth at lower salt levels.…”