[Selective isolation and diversity of acidophilic filamentous actinomycetes from acidic soils].
OBJECTIVE
To establish effective methods for selective isolation of acidophilic filamentous actinomycetes from acidic soils, and to investigate their genus and species diversity.


METHODS
Four pretreatments and 5 media supplemented with different inhibitors were used for isolation. The best combination of methods was determined according to the number and ratio of actinomycete colonies on plates, and was applied to isolate actinomycetes from 17 acidic soil samples collected in Jiangxi Province. The isolates were grouped based on cultural characteristics. The micromorphology and pH growth range of each group were studied to choose the representative isolates, which were subsequently subjected to 16S rRNA gene analysis to investigate their diversity.


RESULTS
We found the best isolation approach involved Dispersion and Differential Centrifugation (DDC) pretreatment and GTV medium supplemented with cycloheximide, nalidixic acid nystatin (each at 50 mg/L). 369 isolates were obtained, and were assigned to 10 color groups. 6.6% of the isolates were strictly acidophilic actinomycetes, 72.4% were neutrotolerant acidophilic actinomycetes, and 21.0% were acidotolerant ones. The 52 representative isolates belong to 12 recognized genera: 30 of them fall within the genus Streptomyces, 6 belong to Micromonospora, 3 belong to Nocardia, 3 belong to Nonomuraea, 2 belong to Kribbella, 2 belong to Microbispora, and the other 6 strains belong to Actinomadura, Amycolatopsis, Dactylosporangium, Lentzea, Planotetraspora and Streptacidiphilus, respectivley. The Streptomyces isolates formed 12 evolutionary groups in the Streptomyces 16S rRNA gene tree.


CONCLUSIONS
The selective isolation approach established here is robust for isolating various acidophilic filamentous actinomycetes from soil. Acidic soils in Jiangxi Province harbor abundant and diverse acidophilic actinomycetes.
Ding
Yun
Y
State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China.
Huang
Ying
Y
Ruan
Jisheng
J
Gao
Yongsheng
Y
D039903:Actinobacteria / Q000145:classification / Q000302:isolation & purification; D000192:Actinomycetales / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D015373:Bacterial Typing Techniques; D004275:DNA, Ribosomal / Q000032:analysis*; D009615:Nocardia / Q000145:classification / Q000235:genetics; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000032:analysis* / Q000235:genetics; D012988:Soil Microbiology; D013302:Streptomyces / Q000145:classification / Q000235:genetics / Q000302:isolation & purification
D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S