Genera Burkholderia and Lipomyces are predominant aluminum-resistant microorganisms isolated from acidic forest soils using cycloheximide-amended growth media

摘要

In acidic forest soils, microorganisms should adapt to toxicity of aluminum (Al), which is solubilized by acidity. We hypothesized that Al-resistant bacteria are diverse, especially in soils with high levels of Al, because these bacteria are expected to have adapted to Al stress over a long time. We isolated Al-resistant bacteria from acid forest soils using diluted tryptic soy broth agar plates with added Al and cycloheximide, and examined the relationship between their diversity and Al levels in soils. Based on 16S rDNA sequences, 10 out of 11 isolated bacteria were assigned to the genus Burkholderia, and 1 to the genus Acinetobacter. Although cycloheximide was added to the Al-enriched agar, yeasts were isolated from soils, and were examined. On the basis of ITS1, 5.8S rDNA, and ITS2 sequences, 13 out of 14 yeast isolates were assigned to Lipomyces sp. and 1 isolate to Cryptococcus sp. Diversity of Al-resistant bacteria was low in acidic forest soils, and was not related to Al levels in soils. Population numbers of Al-resistant microorganisms, however, increased with increasing Al levels.