We obtained 100 isolates of bacteria from deepsea mud samples collected at
various depths (1050-10897m). Various types of bacteria such as alkaliphile
s, thermophiles, psychrophiles, and halophiles were recovered on agar plate
s at a frequency of 0.8 x 10(2) to 2.3 x 10(4)/g of dry sea mud. No acidoph
iles were recovered. These extremophilic bacteria were widely distributed,
being detected at each deep-sea site, and the frequency of isolation of suc
h extremophiles from the deep-sea mud was not directly influenced by the de
pth of the sampling sites. Phylogenetic analysis of deep-sea isolates based
on 16S rDNA sequences revealed that a wide range of taxa were represented
in the deep-sea environments. Growth patterns under high hydrostatic pressu
re were determined for the deep-sea isolates obtained in this study. No ext
remophilic strains isolated in this study showed growth at 60MPa, although
a few of the other isolates grew slightly at this hydrostatic pressure.