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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.
- Diversity and Dynamics of Marine Arenicolous Fungi in Three Seasides of the Korean Peninsula
- Jun Won Lee , Chang Wan Seo , Wonjun Lee , Ji Seon Kim , Ki Hyeong Park , Yoonhee Cho , Young Woon Lim
- J. Microbiol. 2023;61(1):63-82. Published online January 30, 2023
- DOI: https://doi.org/10.1007/s12275-023-00011-1
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- 3 Citations
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Abstract
- Various arenicolous fungal species have been detected from the beach sand in the coastal area. However, little has been revealed regarding their distribution and dynamics. To investigate the overall diversity of marine arenicolous fungi (MAFs) in Korea and whether the composition of MAFs is affected by ocean currents, we isolated and analyzed the fungal community from the western, southern, and eastern seasides of the Korean Peninsula. In total, 603 strains were isolated and identified as 259 species based on appropriate molecular markers for each genus (ITS, BenA, CaM, tef1, and act). The composition of MAFs showed differences among the seasides. Our results indicate that many MAFs inhabit the beach sand on the Korean Peninsula, and the composition of MAFs is also affected by ocean currents flowing along each coast.
- Flaviflexus equikiangi sp. nov. isolated from faeces of Equus kiang (Tibetan wild ass) and carrying a class 1 integron gene cassette in its genome
- Caixin Yang , Xingxing Lian , Yanpeng Cheng , Yifan Jiao , Jing Yang , Kui Dong , Shan Lu , Xin-He Lai , Dong Jin , Han Zheng , Ji Pu , Suping Wang , Liyun Liu , Jianguo Xu
- J. Microbiol. 2022;60(6):585-593. Published online April 18, 2022
- DOI: https://doi.org/10.1007/s12275-022-1673-3
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Abstract
- Two Gram-stain-positive, catalase-negative, non-spore-forming, cocci-shaped strains (dk850T and JY899) were isolated from the feces of Equus kiang in the Qinghai-Tibet Plateau of China. 16S rRNA gene sequence-based phylogenetic analyses showed that strains dk850T and JY899 belong to the genus Flaviflexus, closest to F. salsibiostraticola KCTC 33148T, F. ciconiae KCTC 49253T and F. huanghaiensis H5T. The DNA G + C content of strain dk850T was 62.9%. The digital DNADNA hybridization values of strain dk850T with the closely related species were below the 70% threshold for species demarcation. The two strains grew best at 28°C on brain heart infusion (BHI) agar with 5% sheep blood. All strains had C18:1ω9c and C16:0 as the major cellular fatty acids. MK-9(H4) was the major menaquinone in strain dk850T. The major polar lipids included diphosphatidylglycerol and an unidentified phospholipid. Strains dk850T and JY899 were identified as carrying a class 1 integron containing the aminoglycoside resistance gene aadA11, both strains were resistant to spectinomycin and streptomycin. Based on several lines of evidence from phenotypic and phylogenetic analyses, strains dk850T and JY899 represent a novel species of the genus Flaviflexus, for which the name Flaviflexus equikiangi sp. nov. is proposed. The type strain is dk850T (= CGMCC 1.16593T = JCM 33598T).
- Description of Microbacterium luteum sp. nov., Microbacterium cremeum sp. nov., and Microbacterium atlanticum sp. nov., three novel C50 carotenoid producing bacteria
- Fuquan Xie , Siwen Niu , Xihuang Lin , Shengxiang Pei , Li Jiang , Yun Tian , Gaiyun Zhang
- J. Microbiol. 2021;59(10):886-897. Published online September 7, 2021
- DOI: https://doi.org/10.1007/s12275-021-1186-5
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- 14 Citations
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Abstract
- We have identified three Microbacterium strains, A18JL200T, NY27T, and WY121T, that produce C50 carotenoids. Taxonomy shows they represent three novel species. These strains shared < 98.5% 16S rRNA gene sequence identity with each other and were closely related to Microbacterium aquimaris JCM 15625T, Microbacterium yannicii JCM 18959T, Microbacterium ureisolvens CFH S00084T, and Microbacterium hibisci CCTCC AB 2016180T. Digital DNA-DNA hybridization (dDDH) values and average nucleotide identity (ANI) showed differences among the three strains and from their closest relatives, with values ranging from 20.4% to 34.6% and 75.5% to 87.6%, respectively. These values are below the threshold for species discrimination. Both morphology and physiology also differed from those of phylogenetically related Microbacterium species, supporting that they are indeed novel species. These strains produce C50 carotenoids (mainly decaprenoxanthin). Among the three novel species, A18JL200T had the highest total yield in carotenoids (6.1 mg/L or 1.2 mg/g dry cell weight). Unusual dual isoprenoid biosynthetic pathways (methylerythritol phosphate and mevalonate pathways) were annotated for strain A18JL200T. In summary, we found strains of the genus Microbacterium that are potential producers of C50 carotenoids, but their genome has to be investigated further.
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