Journal of Microbiology

Journal Articles

Delineating the Acquired Genetic Diversity and Multidrug Resistance in Alcaligenes from Poultry Farms and Nearby Soil.: Abhilash Bhattacharjee, Anil Kumar Singh; J. Microbiol. 2024;62(7):511-523. Published online June 21, 2024; DOI: https://doi.org/10.1007/s12275-024-00129-w

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Abstract: Alcaligenes faecalis is one of the most important and clinically significant environmental pathogens, increasing in importance due to its isolation from soil and nosocomial environments. The Gram-negative soil bacterium is associated with skin endocarditis, bacteremia, dysentery, meningitis, endophthalmitis, urinary tract infections, and pneumonia in patients. With emerging antibiotic resistance in A. faecalis, it has become crucial to understand the origin of such resistance genes within this clinically significant environmental and gut bacterium. In this research, we studied the impact of antibiotic overuse in poultry and its effect on developing resistance in A. faecalis. We sampled soil and faecal materials from five poultry farms, performed whole genome sequencing & analysis and identified four strains of A. faecalis. Furthermore, we characterized the genes in the genomic islands of A. faecalis isolates. We found four multidrug-resistant A. faecalis strains that showed resistance against vancomycin (MIC >1000 μg/ml), ceftazidime (50 μg/ml), colistin (50 μg/ml) and ciprofloxacin (50 μg/ml). From whole genome comparative analysis, we found more than 180 resistance genes compared to the reference sequence. Parts of our assembled contigs were found to be similar to different bacteria which included pbp1A and pbp2 imparting resistance to amoxicillin originally a part of Helicobacter and Bordetella pertussis. We also found the Mycobacterial insertion element IS6110 in the genomic islands of all four genomes. This prominent insertion element can be transferred and induce resistance to other bacterial genomes. The results thus are crucial in understanding the transfer of resistance genes in the environment and can help in developing regimes for antibiotic use in the food and poultry industry.

Description of Flavobacterium cyclinae sp. nov. and Flavobacterium channae sp. nov., isolated from the intestines of Cyclina sinensis (Corb shell) and Channa argus (Northern snakehead): Seomin Kang , Jae-Yun Lee , Jeong Eun Han , Yun-Seok Jeong , Do-Hun Gim , Jin-Woo Bae; J. Microbiol. 2022;60(9):890-898. Published online June 22, 2022; DOI: https://doi.org/10.1007/s12275-022-2075-2

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Abstract: Two novel bacterial strains, KSM-R2A25T and KSM-R2A30T, were isolated from intestines of Cyclina sinensis (corb shell) and Channa argus (northern snakehead), respectively. Both specimens were collected in Korea. The strains were Gramstain- negative, non-motile, and strictly aerobic. According to phylogenetic analyses based on 16S rRNA gene sequences, strains belonged to the genus Flavobacterium within the family Flavobacteriaceae. 16S rRNA gene sequences of strains KSMR2A25T and KSM-R2A30T were closely related to Flavobacterium cucumis DSM 18830T and Flavobacterium aquaticum JC164T with sequence similarities of 97.77% and 98.54%, respectively. Further genomic analyses including reconstruction of the UBCG tree and overall genome-related indices suggested them as novel species of the genus Flavobacterium. Both strains contained menaquinone with six isoprene units (MK-6) as a major isoprenoid quinone and iso-C15:1 G, iso- C15:0, and iso-C16:0 as major cellular fatty acids. The major polar lipid in both strains was phosphatidylethanolamine. The genomic G + C contents of strains KSM-R2A25T and KSMR2A30T were 31.7 and 31.9%, respectively. Based on the polyphasic taxonomic study presented here, strains KSM-R2A25T and KSM-R2A30T represent novel species of the genus Flavobacterium, for which the names Flavobacterium cyclinae sp. nov and Flavobacterium channae sp. nov are proposed. The type strains of F. cyclinae sp. nov and F. channae sp. nov are KSM-R2A25T (= KCTC 82978T = JCM 34997T) and KSMR2A30T (= KCTC 82979T = JCM 34998T), respectively.

The synergy effect of arbuscular mycorrhizal fungi symbiosis and exogenous calcium on bacterial community composition and growth performance of peanut (Arachis hypogaea L.) in saline alkali soil: Dunwei Ci , Zhaohui Tang , Hong Ding , Li Cui , Guanchu Zhang , Shangxia Li , Liangxiang Dai , Feifei Qin , Zhimeng Zhang , Jishun Yang , Yang Xu; J. Microbiol. 2021;59(1):51-63. Published online November 17, 2020; DOI: https://doi.org/10.1007/s12275-021-0317-3

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18 Citations

Abstract: Peanut (Arachis hypogaea. L) is an important oil seed crop. Both arbuscular mycorrhizal fungi (AMF) symbiosis and calcium (Ca2+) application can ameliorate the impact of saline soil on peanut production, and the rhizosphere bacterial communities are also closely correlated with peanut salt tolerance; however, whether AMF and Ca2+ can withstand high-salinity through or partially through modulating rhizosphere bacterial communities is unclear. Here, we used the rhizosphere bacterial DNA from saline alkali soil treated with AMF and Ca2+ alone or together to perform high-throughput sequencing of 16S rRNA genes. Taxonomic analysis revealed that AMF and Ca2+ treatment increased the abundance of Proteobacteria and Firmicutes at the phylum level. The nitrogenfixing bacterium Sphingomonas was the dominant genus in these soils at the genus level, and the soil invertase and urease activities were also increased after AMF and Ca2+ treatment, implying that AMF and Ca2+ effectively improved the living environment of plants under salt stress. Moreover, AMF combined with Ca2+ was better than AMF or Ca2+ alone at altering the bacterial structure and improving peanut growth in saline alkali soil. Together, AMF and Ca2+ applications are conducive to peanut salt adaption by regulating the bacterial community in saline alkali soil.

In vitro disinfection efficacy and clinical protective effects of common disinfectants against acute hepatopancreatic necrosis disease (AHPND)-causing Vibrio isolates in Pacific white shrimp Penaeus vannamei: Peizhuo Zou , Qian Yang , Hailiang Wang , Guosi Xie , Zhi Cao , Xing Chen , Wen Gao , Jie Huang; J. Microbiol. 2020;58(8):675-686. Published online July 27, 2020; DOI: https://doi.org/10.1007/s12275-020-9537-1

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Abstract: Acute hepatopancreatic necrosis disease (AHPND) is one of the most significant bacterial diseases in global shrimp culture, causing severe economic losses. In the present study, we carried out in vitro antimicrobial tests to investigate the disinfection efficacy of 14 common disinfectants toward different AHPND-causing Vibrio spp., including eight isolates of V. parahaemolyticus, four isolates of V. campbellii, and one isolate of V. owensii. Polyhexamethylene biguanidine hydrochloride (PHMB) was revealed to possess the strongest inhibitory activity. Through analyzing and evaluating the results of antimicrobial tests and acute toxicity test, we selected PHMB and hydrogen peroxide (H2O2) for further clinical protection test. Clinical manifestations indicated that both PHMB (2 mg/L and 4 mg/L) and H2O2 (12 mg/L) could effectively protect juvenile Penaeus vannamei from the infection of V. parahaemolyticus isolate Vp362 at 106 CFU/ml, and the survival rate was over 80%. When the bacterial concentration was reduced to 105 CFU/ml, 104 CFU/ml, and 103 CFU/ml, the survival rate after treated by 1 mg/L PHMB was 64.44%, 93.33%, and 100%, respectively. According to the results, PHMB and H2O2 showed a lower toxicity while a better protection activity, particularly against a lower concentration of the pathogens. Therefore, these two disinfectants are proved to be promising disinfectants that can be applied to prevent and control AHPND in shrimp culture. Moreover, the methods of this study also provided valuable information for the prevention of other important bacterial diseases and suggested a reliable means for screening potential drugs in aquaculture.

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