Complete Genome Sequence of Thermus aquaticus Y51MC23.

Thermus aquaticus Y51MC23 was isolated from a boiling spring in the Lower Geyser Basin of Yellowstone National Park. Remarkably, this T. aquaticus strain is able to grow anaerobically and produces multiple morphological forms. Y51MC23 is a Gram-negative, rod-shaped organism that grows well between 50°C and 80°C with maximum growth rate at 65°C to 70°C. Growth studies suggest that Y51MC23 primarily scavenges protein from the environment, supported by the high number of secreted and intracellular proteases and peptidases as well as transporter systems for amino acids and peptides. The genome was assembled de novo using a 350 bp fragment library (paired end sequencing) and an 8 kb long span mate pair library. A closed and finished genome was obtained consisting of a single chromosome of 2.15 Mb and four plasmids of 11, 14, 70, and 79 kb. Unlike other Thermus species, functions usually found on megaplasmids were identified on the chromosome. The Y51MC23 genome contains two full and two partial prophage as well as numerous CRISPR loci. The high identity and synteny between Y51MC23 prophage 2 and that of Thermus sp. 2.9 is interesting, given the 8,800 km separation of the two hot springs from which they were isolated. The anaerobic lifestyle of Y51MC23 is complex, with multiple morphologies present in cultures. The use of fluorescence microscopy reveals new details about these unusual morphological features, including the presence of multiple types of large and small spheres, often forming a confluent layer of spheres. Many of the spheres appear to be formed not from cell envelope or outer membrane components as previously believed, but from a remodeled peptidoglycan cell wall. These complex morphological forms may serve multiple functions in the survival of the organism, including food and nucleic acid storage as well as colony attachment and organization.