THE MICROBIAL ECOLOGY OF SOME ITALIAN HOT-SPRING TRAVERTINES

The microbial flora of eight Italian travertine-depositing hot springs is described. At all sites, the flora was dominated by photosynthetic microbes forming two well-defined communities. At temperatures of 10- 40 degrees C and sulphide levels of 50-500 mu M/I a community of the n on-filamentous sulphur bacteria Chlorobium chlorovibrioides, Chromatiu m minus and Thiobacillus spp, predominated. At 40-60 degrees C and sul phide levels of 0-100 mu M/I, a community of the filamentous photosynt hetic bacteria Chloroflexus sp., Lyngbya (Phormidium) laminosum and Sp irulina labyrinthiformis occurred. Other bacteria isolated included De sulphovibrio cf. thermophilus, Thiosphaera sp. and Oscillatoria. The c ommunities have not previously been recognized in European thermal wat ers. None of the bacteria was restricted to travertine-depositing wate rs but Spirulina has been widely reported from warm, calcium-rich site s. The distribution of these bacteria was influenced most by sulphide and temperature. Although some travertine fabrics were clearly modifie d by the presence of bacteria, a direct influence of bacterial metabol ism on travertine formation remains to be established at these sites. Measurements of temperature, pH, E(h), dissolved oxygen, carbon dioxid e, Ca, Mg, Na and sulphate are provided.