Chiang Mai Journal of Science

  Diversity and isolation of actinomycetes from marine sediments collected from the South China Sea at depths ranging from 34 to 3,235 m were carried using dilution plate technique with heat and non-heat pretreatment on 9 isolation media, and plate stamping technique incubated on RH and M6 media at 28 °C and 10 °C.  A total of 43 actinomycete strains were isolated from the different depth of marine sediments, among of which 32 were from the deep sea samples (1,645-3,235 m). Non-heat pretreatment was effective for the actinomycete isolation from deep sea sediment samples. RH and M6 were the more effective media regarding the number and diversity of isolates recovered. A higher percentage of actinomycete colonies (19.64%) were obtained by using plate stamping technique comparing to dilution plate method (5.29%). However, low-temperature incubation (10 °C) was also significantly effective on actinomycetes isolation from deep-sea samples with a higher percentage of the ratio actinomycetes to other total viable bacteria.  Higher diversity of actinomycetes genera were found in deep-sea regions (depth 1,645 m-3,235 m) comparing to shallow regions marine sediments (depth <200 m). Partial 16S rRNA gene sequence data revealed that the isolates belong to the Class Actinobacteria, with genetic affiliations to five orders, six families, and six genera. Micromonospora (n= 23) and Streptomyces (n= 14) were the dominant genera, followed by Dietzia (n= 2), Tsukamurella (n=2), Blastococcus (n=1) and Microbacterium (n=1).