Bacterial Activity and Their Physiological Characteristics in the Sediments of O DP Holes 1202A and 1202D, Okinawa Trough, Western Pacific



Bacterial strains were isolated and identified from the down-core sediments of Site 1202 of ODP Leg 195 in the Okinawa Trough. Their phylogenetic relationships and physiological characteristics were determined. The isolates were cultured in aerobic and anaerobic sulfate-reducing and fermentative media at temperatures of 30¢XC and 45¢XC. The results showed that there were gram-positive/negative rod- and/or sphere-shaped bacteria in the sediments at all depths from 3 to 358.3 meters below the seafloor (mbsf), but no bacteria were present at depths greater than 358.3 mbsf (> 64.73 ka in age of sediment) were isolated (maximum core depth 406.5 mbsf). On the basis of the nucleotide similarities of 16S rDNA and reconstructed phylogeny, the bacterial isolates of the sediments of 10.1 mbsf (1202A002H) and 241.2 mbsf (1202D027X) were shown to share high identities with the Bacillus subtilis and Pseudomonas putida or _?¶_n-proteobacterium MPD-98 strains. Physiological experiments showed that the optimal temperature growth of the studied bacteria was 30¢XC but the bacteria obtained at some depths could tolerate temperatures up to 45¢XC. The maximum salinity allowed for the growth of the cultured bacteria was 60 ¡V 650/00. The optimal pH for bacterial growth was 7.0 - 8.3. None of the bacteria extracted from the studied sediments could survive at pH ≤_n5 or ≥_n11. These halotolerant bacteria were capable of making consumption of Fe, Cu2+ , Na+, K+, Mg2+ , Ca2+, and F−, but no biogenic minerals could be identified in the present study.

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