• Journal of Microbiology and Biotechnology
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• v.30 no.9
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• pp.1367-1378
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• 2020

The polyphagous eri silk moth, Samia ricini, is associated with various symbiotic gut bacteria believed to provide several benefits to the host. The larvae of S. ricini were subjected to isolation of gut bacteria using culture-dependent 16S rRNA generic characterization, metagenomics analysis and qualitative enzymatic assays. Sixty culturable aerobic gut bacterial isolates comprising Firmicutes (54%) and Proteobacteria (46%); and twelve culturable facultative anaerobic bacteria comprising Proteobacteria (92%) and Firmicutes (8%) were identified inhabiting the gut of S. ricini. The results of metagenomics analysis revealed the presence of a diverse community of both culturable and un-culturable gut bacteria belonging to Proteobacteria (60%) and Firmicutes (20%) associated with seven orders. An analysis of the results of culturable isolation indicates that these bacterial isolates inhabited all the three compartments of the gut. Investigation on persistence of bacteria coupled with metagenomics analysis of the fifth instar suggested that bacteria persist in the gut across the different instar stages. In addition, enzymatic assays indicated that 48 and 75% of culturable aerobic, and 75% of anaerobic gut bacterial isolates had cellulolytic, lipolytic and nitrate reductase activities, thus suggesting that they may be involved in food digestion and nutritional provision to the host. These bacterial isolates may be good sources for profiling novel genes and biomolecules for biotechnological application.

• The Korean Journal of Pesticide Science
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• v.19 no.3
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• pp.279-286
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• 2015

Cotesia plutellae bracovirus (CpBV) is a polydnavirus symbiotic to C. plutellae parasitizing young larvae of the diamondback moth, Plutella xylostella. Several CpBV genes play important roles in suppressing immune responses of the parasitized larvae. This study tested a hypothesis that the CpBV genes inducing host immunosuppression could be applied to develop a potent recombinant baculovirus. Based on a previous study, a recombinant baculovirus expressing CpBV-ELP1 (AcMNPV-ELP1) was selected and multiplied using larvae of the beet armyworm, Spodoptera exigua. The recombinant viruses were produced in a yield of $5{\times}10^{10}$ polyhedral inclusion body (PIB)/larva. The cultured AcMNPV-ELP1 exhibited a much higher pathogenicity against S. exigua larvae. However, its insecticidal activity was varied among larval instars of S. exigua, in which first and late instars were high susceptible. Spray of the recombinant baculovirus ($5{\times}10^6PIB/mL$) exhibited higher control efficacy (${\approx}$ 88%) against S. exigua larvae infesting cabbage than a chemical insecticide, tebufenozide, at 7 days after treatment. These results indicate that AcMNPV-ELP1 mass-cultured using host insect system is highly pathogenic and can be applied to develop a novel microbial control agent.

• Journal of Life Science
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• v.26 no.6
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• pp.711-720
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• 2016

To determine the degree of common genes and the phylogenetic relationships among genome-sequenced 680 prokaryotes, the similarities among 4,631 clusters of orthologous groups of protein (COGs)’ presence/ absence and gene content trees were analyzed. The number of COGs was in the range of 103–2,199 (mean 1377.1) among 680 prokaryotes. Candidatus Nasuia deltocephalinicola str. NAS-ALF, an obligate symbiont with insects, showed the minimum COG, while Pseudomonas aeruginosa PAO1, an opportunistic pathogen, represented the maximum COG. The similarities between two prokaryotes were 49.30–99.78 % (mean 72.65%). Methanocaldococcus jannaschii DSM 2661 (hyperthermophilic and autotrophic, Euryarchaeota phylum) and Mesorhizobium loti MAFF303099 (mesophilic and symbiotic, alpha-Proteobacteria class) had the minimum amount of similarities. As gene content may represent the potential for an organism to adapt to each habitat, this may represent the history of prokaryotic evolution or the range of prokaryotic habitats at present on earth. COG content trees represented the following. First, two members of Chloroflexi phylum (Dehalogenimonas lykanthroporepellens BL-DC-9 and Dehalococcoides mccartyi 195) showed a greater relationship with Archaea than other Eubacteria. Second, members of the same phylum or class in the 16S rRNA gene were separated in the COG content tree. Finally, delta- and epsilon-Proteobacteria were in different lineages with other Proteobacteria classes in neighbor-joining (NJ) and maximum likelihood (ML) trees. The results of this study would be valuable to identifying the origins of organisms, functional relationships, and useful genes.