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- The β‑Lactamase Activity at the Community Level Confers β‑Lactam Resistance to Bloom‑Forming Microcystis aeruginosa Ce
- Yerim Park , Wonjae Kim , Minkyung Kim , Woojun Park
- J. Microbiol. 2023;61(9):807-820. Published online October 18, 2023
- DOI: https://doi.org/10.1007/s12275-023-00082-0
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- 5 Citations
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Abstract
- Many freshwater cyanobacteria, including Microcystis aeruginosa, lack several known antibiotic resistance genes; however, both axenic and xenic M. aeruginosa strains exhibited high antibiotic resistance against many antibiotics under our tested concentrations, including colistin, trimethoprim, and kanamycin. Interestingly, axenic PCC7806, although not the xenic NIBR18 and NIBR452 strains, displayed susceptibility to ampicillin and amoxicillin, indicating that the associated bacteria in the phycosphere could confer such antibiotic resistance to xenic strains. Fluorescence and scanning electron microscopic observations revealed their tight association, leading to possible community-level β-lactamase activity. Combinatory treatment of ampicillin with a β-lactamase inhibitor, sulbactam, abolished the ampicillin resistance in the xenic stains. The nitrocefin-based assay confirmed the presence of significant community-level β-lactamase activity. Our tested low ampicillin concentration and high β-lactamase activity could potentially balance the competitive advantage of these dominant species and provide opportunities for the less competitive species, thereby resulting in higher bacterial diversity under ampicillin treatment conditions. Non-PCR-based metagenome data from xenic NIBR18 cultures revealed the dominance of blaOXArelated antibiotic resistance genes followed by other class A β-lactamase genes (AST-1 and FAR-1). Alleviation of ampicillin toxicity could be observed only in axenic PCC7806, which had been cocultured with β-lactamase from other freshwater bacteria. Our study suggested M. aeruginosa develops resistance to old-class β-lactam antibiotics through altruism, where associated bacteria protect axenic M. aeruginosa cells.
- Martelella lutilitoris sp. nov., isolated from a tidal mudflat
- Young-Ju Kim , Soon Dong Lee
- J. Microbiol. 2019;57(11):976-981. Published online September 25, 2019
- DOI: https://doi.org/10.1007/s12275-019-9259-4
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- 8 Citations
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Abstract
- A novel, Gram-stain-negative, marine bacterium, designated GH2-6T, was isolated from a rhizosphere mudflat of a halophyte (Carex scabrifolia) collected in Gangwha Island, the Republic of Korea. The cells of the organism were strictly aerobic, oxidase- and catalase-positive, non-flagellated rods. Growth occurred at 20–45°C, pH 5–10, and 0.5–9 (w/v) NaCl. The requirement of Na+ for growth (0.5–3%) was observed. The major respiratory quinone was Q-10. The major polar lipids were phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, an aminolipid and a glycolipid. The predominant fatty acids were C18:1 ω7c, C18:0, C16:0, C19:0 cyclo ω8c, C18:1 ω7c 11-methyl and summed feature 2 (C14:0 3-OH and/or C16:1 iso I). The genome size was 4.45 Mb and the G+C content of the genomic DNA was 61.9 mol%. Phylogenetic analyses based on 16S rRNA gene sequences revealed that strain GH2-6T belonged to genus Martelella and formed a tight cluster with M. radicis BM5-7T and M. endophytica YC6887T. Levels of 16S rRNA gene sequence similarity between the novel isolate and members of the genus were 99.3–95.5%, but strain GH2-6T possessed an extended loop (49 nucleotides in length) between positions 187 and 213 of the 16S rRNA gene sequence (E. coli numbering). DDH values in vitro between the novel isolate and the closest relatives were 23.2±12.8 – 46.3±5.2%. On the basis of polyphasic data presented in this study, the type strain GH2-6T (= KACC 19403T = KCTC 62125T = NBRC 113212T) represents a novel species of the genus Martelella for which the name Martelella lutilitoris sp. nov. is proposed.
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