Newly isolated Chl d-containing cyanobacteria

Abstract

Stromatolites are sedimentary structures formed by microbial mats that are typically found in limestone-or dolostone-rich environments. Shark Bay, Australia, has abundant examples of living marine stromatolites. Although the stromatolites from Shark Bay are only about 2000–3000 years old, they are similar to fossilized evidence of life found on Earth up to 3.5 billion years ago. Using infra-red light centred at 720 nm, new chlorophyll d-containing microorganisms were isolated from the living stromatolites (collected from Shark Bay, Western Australia) and red algae on mangrove pneumatophores (collected from the Georges River, Sydney, Australia) and enriched in KES+ seawater medium. Microscopic examination of the red-light enriched cultures confirmed that they are Acaryochloris-like cyanobacteria. Using cyanobacterial-specific 16S rRNA gene primers, we obtained almost full length sequences of 16S rDNA from the newly isolated Chl d-containing cyanobacteria. The sequences shared 98% identity with Acaryochloris marina MBIC11017. Interestingly, the strain isolated from stromatolites (designated as “ssball1” strain) was more similar to Acaryochloris sp CR111A while the strain isolated from Georges River (designated as “Mangrove1” strain) was more closely related to Acaryochloris sp CCMEE 5401, which was isolated from an inland “lake”, Salton Sea in California,. Pigment composition of the newly isolated strains were determined using HPLC, However, no obvious differences were noted. Chl d was the major photopigment while Chl a was present as a minor photopigment, about 2%–3.5 % of the total chlorophyll.