Microbial diversity of extant stromatolites in the hypersaline marine environment of Shark Bay, Australia

Abstract

Stromatolites have been present on Earth, at various levels of distribution and diversity, for more than 3 billion years. Today, the best examples of stromatolites forming in hypersaline marine environments are in Hamelin Pool at Shark Bay, Western Australia. Despite their evolutionary significance, little is known about their associated microbial communities. Using a polyphasic approach of culture-dependent and culture-independent methods, we report the discovery of a wide range of microorganisms associated with these biosedimentary structures. There are no comparable reports combining these methodologies in the survey of cyanobacteria, bacteria, and archaea in marine stromatolites. The community was characterized by organisms of the cyanobacterial genera Synechococcus, Xenococcus, Microcoleus, Leptolyngbya, Plectonema, Symploca, Cyanothece, Pleurocapsa and Nostoc. We also report the discovery of potentially free-living Prochloron. The other eubacterial isolates and clones clustered into seven phylogenetic groups: OP9, OP10, Marine A group, Proteobacteria, Low G+C Gram-positive, Planctomycetes and Acidobacteria. We also demonstrate the presence of sequences corresponding to members of halophilic archaea of the divisions Euryarchaeota and Crenarchaeota and methanogenic archaea of the order Methanosarcinales. This is the first report of such archaeal diversity from this environment. This study provides a better understanding of the microbial community associated with these living rocks.

Determining the specific microbial populations and their spatial distribution within the stromatolite ecosystem of Shark Bay

“…High net evaporation rates and average water temperatures throughout the year between 17 and 27 1C create a hypersaline environment with at least twice the salinity of seawater (Arp et al, 2001). Intertidal columnar stromatolites ( Figure 1) were collected during the (Burns et al (2004)) and (d) a slide of sample HPS2. Both (c) and (d) were embedded in epoxy resin and sectioned to a width of 30 mm; photograph taken using light microscopy (magnification ¼ Â 4).…”

“…In addition, both heterotrophic aerobic and anaerobic bacteria, which synthesize low-molecular weight organic compounds and amorphous exopolymers, were also present in these structures (Visscher et al, 1998). In contrast to the Bahaman stromatolites, the Shark Bay communities exhibit a greater diversity of archaea, cyanobacteria and heterotrophic bacteria (Burns et al, 2004;Papineau et al, 2005;Leuko et al, 2007). Shark Bay stromatolite communities are characterized by cyanobacteria belonging to the genera Synechococcus, Xenococcus, Microcoleus, Leptolyngbya, Plectonema, Symploca, Cyanothece, Pleurocapsa, Nostoc and Prochloron (Burns et al, 2004;Papineau et al, 2005).…”

“…In contrast to the Bahaman stromatolites, the Shark Bay communities exhibit a greater diversity of archaea, cyanobacteria and heterotrophic bacteria (Burns et al, 2004;Papineau et al, 2005;Leuko et al, 2007). Shark Bay stromatolite communities are characterized by cyanobacteria belonging to the genera Synechococcus, Xenococcus, Microcoleus, Leptolyngbya, Plectonema, Symploca, Cyanothece, Pleurocapsa, Nostoc and Prochloron (Burns et al, 2004;Papineau et al, 2005). These initial studies identified more than 20 of the 52 known divisions of bacteria, as well as archaeal communities, including both Euryarchaeota and Crenarchaeota gene sequences.…”

“…Comparison between stromatolites of differing morphology was also related to specific changes in the microbial community present. Recent studies on both Shark Bay and Bahaman stromatolites have revealed that eukaryotes are scarce in these formations Burns et al, 2004;Papineau et al, 2005), though a variety of flagellates have been documented from Shark Bay (Al-Qassab et al, 2002). It has been proposed that stromatolites thrive in environments that exclude many higher organisms, particularly those that may graze on the resident microorganisms.…”

A Review on Microbialites: a Korean Perspective

“…따라서 지질 시대에 따라 석회화 된 미생물의 분포가 다른 것은 그 시대에 어떤 미생 물이 살았느냐 보다는 해수 및 대기 조성의 변화 등 전반적인 환경 조건에 더 크게 영향을 받은 결과일 것이다. 현생 미생물암에는 시아노박테리아뿐만 아니라 세 균(bacteria), 고세균(archaea), 녹조류(green algae), 규조류(diatoms), 균류(fungi) 등 다양한 종류의 미생 물이 존재하며 이들이 함께 미생물암을 생성하는 것 으로 생각된다 Burns et al, 2004;Papineau et al, 2005). 하지만 현생 미생물암 은 과거 여러 지질시대의 미생물암들과는 그 중간 및 미세구조가 다르므로 이들을 직접 비교하는 것은 어 렵다 (Riding, 2000(Riding, , 2011b.…”