Iron-Tolerant Cyanobacteria as an Effective Tool to Study Early Evolution of Life and the Development of Biosignatures

What is the diversity of cyanobacteria in iron-depositing hot springs? We are currently conducting preliminary studies on the diversity of iron-tolerant CB isolated from irondepositing hot springs in and around Yellowstone National Park (WY, USA). Molecular analysis has confirmed the prediction [1] that the diversity of iron-tolerant CB is ill-defined. Analysis of 16S rRNA sequences from 15 unialgal isolates of iron-tolerant CB indicate that 7 species have only 93 to 95% similarity to published sequences. Several iron-tolerant isolates, including Chroogloeocystis siderophila, likely represents a new CB genera [1]. On the other hand, preliminary fingerprinting of unialgal isolates from Chocolate Pots Hot Spring shows the presence of such widespread genus as Fischerella. Relatively high abundance of unidentified CB species in irondepositing hot springs could suggest that iron tolerance in CB is determined by their relation to specific lineages of CB. The presence of such species as Fischerella in irondepositing hot springs may, however, suggest that there is no strong restriction on the occupation of this unique niche by originally non iron-tolerant CB. Thus, broad-scaled studies of the diversity of CB in iron-depositing hot springs, and the evaluation of the ratio between the quantity of unidentified CB and the quantity of species common to hot springs in general, could give clues as to whether contemporary CB derive from lineages of ancestral cyanobacteria or whether they have enhanced abilities to occupy a niche containing elevated iron.