• Korean Journal of Microbiology
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• v.53 no.4
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• pp.309-315
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• 2017

Most of acidophiles are found in the various low pH environments and affect to metal cycle through oxidation and reduction reactions. The present study was carried out above 50 strains as acidophiles isolated from acidic soils of exhausted mine and Jeju Gotjawal. Finally, total 19 strains obtained and were tentatively identified based on comparative similarity analysis for 16S rRNA gene sequence and physiological characterizations. These isolates belonged to Gammaproteobacteria (6 strains), Actinobacteria (5 strains), Betaproteobacteria (4 strains), Alphaproteobacteria (2 strains), and Bacilli (2 strains). We observed that these isolates can grow under low pH culture condition. This case study for analysis physiological characterizations of indigenous microorganisms in acidic soil might provide basic information on useful application.

• Journal of Microbiology and Biotechnology
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• v.27 no.4
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• pp.649-659
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• 2017

Extremophilic microorganisms have established a diversity of molecular strategies in order to survive in extreme conditions. Biocatalysts isolated by these organisms are termed extremozymes, and possess extraordinary properties of salt allowance, thermostability, and cold adaptivity. Extremozymes are very resistant to extreme conditions owing to their great solidity, and they pose new opportunities for biocatalysis and biotransformations, as well as for the development of the economy and new line of research, through their application. Thermophilic proteins, piezophilic proteins, acidophilic proteins, and halophilic proteins have been studied during the last few years. Amylases, proteases, lipases, pullulanases, cellulases, chitinases, xylanases, pectinases, isomerases, esterases, and dehydrogenases have great potential application for biotechnology, such as in agricultural, chemical, biomedical, and biotechnological processes. The study of extremozymes and their main applications have emerged during recent years.

• Journal of Microbiology
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• v.44 no.6
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• pp.600-606
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• 2006

Spore forming actinobacteria (sporoactinobacteria) isolated from soils with an acidic pH in Pinus thunbergii forests and coal mine waste were subjected to taxonomic characterization. For the isolation of acidophilic actinobacteria, acidified starch casein agar (pH adjusted to 4-5) was used. The numbers of actinobacteria growing in acidic media were between $3.2{\times}10^4$ and $8.0{\times}10^6$ CFU/g soil. Forty three acidophilic actinobacterial strains were isolated and their 16S rDNA sequences were determined. The isolates were divided into eight distinctive phylogenetic clusters within the variation encompassed by the family Streptomycetaceae. Four clusters among them were assigned to the genus Streptacidiphilus, whereas the remaining four were assigned to Streptomyces. The clusters belonging to either Streptomyces or Streptacidiphilus did not form a monophyletic clade. The growth pH profiles indicated that the representative isolates grew best between pH 5 and 6. It is evident from this study that acidity has played a critical role in the differentiation of the family Streptomycetaceae, and also that different mechanisms might have resulted in the evolution of two groups, Streptacidiphilus (strict acidophiles) and neutrotolerant acidophilic Streptomyces. The effect of geographic separation was clearly seen among the Streptacidiphilus isolates, which may be a key factor in speciation of the genus.

• Korean Journal of Microbiology
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• v.55 no.3
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• pp.248-257
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• 2019

In this study, we isolated about 70 bacterial strains from terrestrial and marine environments in Jeju island, and finally, total 21 strains were obtained based on the 16S ribosomal RNA gene sequence analysis. These isolated strains were classified into 16 genera of 5 classes and were identified as an unrecorded species in the Republic of Korea. As a result of the substrate utilization and capability for polymer degradation, the physiological phenotypes for acid resistance and halophilic bacteria were observed to be distinct from each other, except for some acid resistance strains. This study might provide basic information on utilization for indigenous microorganisms.

• Journal of Microbiology and Biotechnology
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• v.32 no.9
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• pp.1110-1119
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• 2022

Fe-S clusters are versatile and essential cofactors that participate in multiple and fundamental biological processes. In Escherichia coli, the biogenesis of these cofactors requires either the housekeeping Isc pathway, or the stress-induced Suf pathway which plays a general role under conditions of oxidative stress or iron limitation. In the present work, the Fe-S cluster assembly Isc and Suf systems of acidophilic Bacteria and Archaea, which thrive in highly oxidative environments, were studied. This analysis revealed that acidophilic microorganisms have a complete set of genes encoding for a single system (either Suf or Isc). In acidophilic Proteobacteria and Nitrospirae, a complete set of isc genes (iscRSUAX-hscBA-fdx), but not genes coding for the Suf system, was detected. The activity of the Isc system was studied in Leptospirillum sp. CF-1 (Nitrospirae). RT-PCR experiments showed that eight candidate genes were co-transcribed and conform the isc operon in this strain. Additionally, RT-qPCR assays showed that the expression of the iscS gene was significantly up-regulated in cells exposed to oxidative stress imposed by 260 mM Fe₂(SO₄)₃ for 1 h or iron starvation for 3 h. The activity of cysteine desulfurase (IscS) in CF-1 cell extracts was also upregulated under such conditions. Thus, the Isc system from Leptospirillum sp. CF-1 seems to play an active role in stressful environments. These results contribute to a better understanding of the distribution and role of Fe-S cluster protein biogenesis systems in organisms that thrive in extreme environmental conditions.