Antimicrobial activities of Antarctic soil microbes from Deception island

第6回極域科学シンポジウム[OB] 極域生物圏11月16日（月）　国立極地研究所１階交流アトリウ

Isolation and characterization of Antarctic psychrotroph Streptomyces sp. strain INACH3013

An actinobacterial strain with antimicrobial activity, INACH3013, was isolated from soil collected from Antarctica. The taxonomic status of the isolate was established using a polyphasic approach. The strain was identified as belonging to the genus Streptomyces based on the scanning electron microscopic observation and partial 16S rRNA gene sequence analysis. The sequence analysis revealed that strain INACH3013 is closely related to Streptomyces fildesensis (99.8%), S. beijiangensis (98.1%) and S. purpureus (97.2%). A phylogenetic tree constructed using the partial 16S rRNA gene sequences of strain INACH3013 and closely related strains revealed that INACH3013 fell into the same subclade as S. fildesensis and S. purpureus. Strain INACH3013 was observed to be psychrotolerant, slightly halotolerant (up to 5% NaCl) and capable of inhibiting the growth of seven Gram-negative and eight Gram-positive foodborne pathogens. The GenBank/EMBL/DDBJ accession number for the 16S rRNA gene sequence of the strain is KJ624755

A Talaromyces fungal species with strong antimicrobial activity from Deception Island, Antarctica

Deception Island is well-known for harboring highly diverse microbial communities due to its unique volcanic environment in Antarctica. Most studies focused on bacteria, and relatively little was known about the fungal species on this island. The present study was aimed to determine the antimicrobial production and nutrient utilization profiles of a soil fungus from Deception Island, designated as Im33. Our findings showed that the strain had maximum mycelial growth and sporulation on malt-extract agar (MEA) medium, but it demonstrated the strongest antimicrobial activity in yeast extract-malt extract broth (YMB) medium. Phylogenetic analysis of the internal transcribed spacer 1 and 2 regions showed that it is a species belonging to the genus Talaromyces. It was resistant to cycloheximide concentrations up to 1,000 mg/L and exhibited broad-spectrum antimicrobial activity against Gram-positive and Gram-negative test pathogens, as well as being able to utilize a variety of carbon sources. This is the first report of a Talaromyces species from Deception Island. The capability of the strain to produce broad-spectrum antimicrobial compounds and various enzymes indicated that Antarctic fungi, like their bacterial counterparts, have adopted various adaptation strategies to compete and survive in the extreme environment

Draft genome sequence of antarctic psychrotroph Streptomyces fildesensis strain INACH3013, isolated from King George Island soil

The draft genome sequence of Streptomyces fildesensis strain INACH3013, a psychrotrophic bacterium isolated from Northwest Antarctic soil, was reported. The genome sequence totaling 9,306,785 bp resulted from 122 contigs characterized by a GC content of 70.55%

A Talaromyces Fungal Species with Strong Antimicrobial Activity from Deception Island, Antarctica

Deception Island is well-known for harboring highly diverse microbial communities due to its unique volcanic environment in Antarctica. Most studies focused on bacteria, and relatively little was known about the fungal species on this island. The present study was aimed to determine the antimicrobial production and nutrient utilization profiles of a soil fungus from Deception Island, designated as Im33. Our findings showed that the strain had maximum mycelial growth and sporulation on malt-extract agar (MEA) medium, but it demonstrated the strongest antimicrobial activity in yeast extract-malt extract broth (YMB) medium. Phylogenetic analysis of the internal transcribed spacer 1 and 2 regions showed that it is a species belonging to the genus Talaromyces. It was resistant to cycloheximide concentrations up to 1,000 mg/L and exhibited broad-spectrum antimicrobial activity against Gram-positive and Gram-negative test pathogens, as well as being able to utilize a variety of carbon sources. This is the first report of a Talaromyces species from Deception Island. The capability of the strain to produce broad-spectrum antimicrobial compounds and various enzymes indicated that Antarctic fungi, like their bacterial counterparts, have adopted various adaptation strategies to compete and survive in the extreme environment

Analysis of bacterial communities of King George and Deception Islands, Antarctica using high-throughput sequencing

King George Island (KGI) and Deception Island (DCI) are members of the South Shetland Islands in Antarctica, each with their own landscape and local environmental factors. Both sites are suitable for longterm monitoring of bacterial diversity shift due to warming, as temperature rises relatively faster than East Antarctica. This study was conducted to determine and compare the baseline diversity of soil bacteria in KGI and DCI. 16S rDNA amplicons of bacteria from both sites were sequenced using Illumina next generation sequencer. Results showed that major phyla in KGI and DCI were Actinobacteria, Proteobacteria, Chloroflexi, Verrucomicrobia, Bacteriodetes and Acidobacteria. The distribution and evenness of the soil bacterial communities varied at genus level. The genera Sphingomonas sp. was predominant at both sites while the subsequent six major genera differed. Two bacterial genera, Legionella and Clostridium were also found in low abundance in both sites, both of which may contain pathogenic members. Further verification will be required to determine whether the pathogenic members of these genera are present in both sites

Guidelines for the use and interpretation of assays for monitoring autophagy

In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field