Abstract:
The bacterial diversity of Siloam hot water spring was determined using 454 pyrosequencing of two 16S
rRNA variable regions V1-3 and V4-7. Analysis of the community DNA revealed that the phyla
Proteobacteria, Cyanobacteria, Bacteriodetes, Planctomycetes, Firmicutes, Chloroflexi and
Verrucomicrobia were the most abundant. The bacterial diversity detectable and classifiable was
greater when the V4-7 variable region was used compared to the V1-3 region. The most abundant
bacteria genera detected with region V1-3 were; Stenotrophomonas (23.3%), Aquaspirillum (5.11%),
Zavarzinella (2.73%), Haliscomenobacteria (1.25%), Rheinheimera (1.14%) and Tepidomonas (1.14%). All
the other detectable genera were below 0.6%. Genera detected with region V4-7 from most abundant
were; Stenotrophomonas (17.96%), Zavarzinella (5.81%), Aquaspirillum (4.75%), Rheinheimera (3.52%),
GPI (1.41%), Gemmata (1.41%) and Syntrophobacter (1.06%). All the other genera detected were below
0.7%. Siloam is one of the hottest thermal springs in South Africa (63°C), the water has a pH of 9.5 and
is relatively high in fluoride and bromide; it is possible that the physicochemical properties could have
some influence on the diversity of bacteria. This article reports on the first phylogenetic analysis of a
South African thermal spring bacterial community.