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.

Quorum Quenching Potential of Reyranella sp. Isolated from Riverside Soil and Description of Reyranella humidisoli sp. nov.: Dong Hyeon Lee, Seung Bum Kim; J. Microbiol. 2024;62(6):449-461. Published online May 30, 2024; DOI: https://doi.org/10.1007/s12275-024-00131-2

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Abstract: Quorum quenching refers to any mechanism that inhibits quorum sensing processes. In this study, quorum quenching activity among bacteria inhabiting riverside soil was screened, and a novel Gram-stain-negative, rod shaped bacterial strain designated MMS21-HV4-11(T), which showed the highest level of quorum quenching activity, was isolated and subjected to further analysis. Strain MMS21-HV4-11(T) could be assigned to the genus Reyranella of Alphaproteobacteria based on the 16S rRNA gene sequence, as the strain shared 98.74% sequence similarity with Reyranella aquatilis seoho-37(T), and then 97.87% and 97.80% sequence similarity with Reyranella soli KIS14-15(T) and Reyranella massiliensis 521(T), respectively. The decomposed N-acyl homoserine lactone was restored at high concentrations under acidic conditions, implying that lactonase and other enzyme(s) are responsible for quorum quenching. The genome analysis indicated that strain MMS21-HV4-11(T) had two candidate genes for lactonase and one for acylase, and expected protein structures were confirmed. In the quorum sensing inhibition assay using a plant pathogen Pectobacterium carotovorum KACC 14888, development of soft rot was significantly inhibited by strain MMS21-HV4-11(T). Besides, the swarming motility by Pseudomonas aeruginosa PA14 was significantly inhibited in the presence of strain MMS21-HV4-11(T). Since the isolate did not display direct antibacterial activity against either of these species, the inhibition was certainly due to quorum quenching activity. In an extended study with the type strains of all known species of Reyranella, all strains were capable of degrading N-acyl homoserine lactones (AHLs), thus showing quorum quenching potential at the genus level. This is the first study on the quorum quenching potential and enzymes responsible in Reyranella. In addition, MMS21-HV4-11(T) could be recognized as a new species through taxonomic characterization, for which the name Reyranella humidisoli sp. nov. is proposed (type strain = MMS21-HV4-11( T) = KCTC 82780( T) = LMG 32365(T)).

Effects of Phosphorus‑dissolving Dark Septate Endophytes on the Growth of Blueberry: Qixin Luo , Rui Hou , Xiaojing Shang , Si Li; J. Microbiol. 2023;61(9):837-851. Published online October 5, 2023; DOI: https://doi.org/10.1007/s12275-023-00080-2

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Abstract: Dark septate endophytes (DSEs) are widely distributed and improve plant growth. DSEs secrete large amounts of enzymes to mineralize insoluble phosphorus in soil and convert it into soluble phosphorus, promoting plant uptake of phosphorus. However, the effects of DSEs with phosphate-solubilizing ability on host plants need further study. In this study, phosphorusdissolving DSEs were screened for growth-promoting effects. We isolated, identified and characterized three DSE species (Thozetella neonivea, Pezicula ericae and Hyaloscyphaceae sp.) showing phosphate-solubilizing ability. The impact of single, dual or triple inoculation of DSEs on blueberry plant characteristics was studied. Their effects on colonization intensity, seedling biomass, nutrients in plants and soil, and activities of plant resistance enzymes and soil enzymes were markedly upregulated relative to the control (P < 0.05). The available phosphorus and acid phosphatase levels in different combinations were significantly increased. These findings indicate that the application of the three DSEs may be valuable in facilitating the cultivation of blueberry with a higher biomass and improved plant quality.

Gut Lactobacillus and Probiotics Lactobacillus lactis/rhamnosis Ameliorate Liver Fibrosis in Prevention and Treatment: Sung Min Won , Na Young Lee , Ki&# , Haripriya Gupta , Satya Priya Sharma , Kyung Hwan Kim , Byoung Kook Kim , Hyun Chae Joung , Jin Ju Jeong , Raja Ganesan , Sang Hak Han , Sang Jun Yoon , Dong Joon Kim , Ki Tae Suk; J. Microbiol. 2023;61(2):245-257. Published online February 6, 2023; DOI: https://doi.org/10.1007/s12275-023-00014-y

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5 Citations

Abstract: The progression and exacerbation of liver fibrosis are closely related to the gut microbiome. It is hypothesized that some probiotics may slow the progression of liver fibrosis. In human stool analysis [healthy group (n = 44) and cirrhosis group (n = 18)], difference in Lactobacillus genus between healthy group and cirrhosis group was observed. Based on human data, preventive and therapeutic effect of probiotics Lactobacillus lactis and L. rhamnosus was evaluated by using four mice fibrosis models. L. lactis and L. rhamnosus were supplied to 3,5-diethoxycarbonyl-1,4-dihydrocollidine or carbon tetrachloride-induced liver fibrosis C57BL/6 mouse model. Serum biochemical measurements, tissue staining, and mRNA expression in the liver were evaluated. The microbiome was analyzed in mouse cecal contents. In the mouse model, the effects of Lactobacillus in preventing and treating liver fibrosis were different for each microbe species. In case of L. lactis, all models showed preventive and therapeutic effects against liver fibrosis. In microbiome analysis in mouse models administered Lactobacillus, migration and changes in the ratio and composition of the gut microbial community were confirmed. L. lactis and L. rhamnosus showed preventive and therapeutic effects on the progression of liver fibrosis, suggesting that Lactobacillus intake may be a useful strategy for prevention and treatment.

Characteristic alterations of gut microbiota in uncontrolled gout: Asad ul-Haq , Kyung-Ann Lee , Hoonhee Seo , Sukyung Kim , Sujin Jo , Kyung Min Ko , Su-Jin Moon , Yun Sung Kim , Jung Ran Choi , Ho-Yeon Song , Hyun-Sook Kim; J. Microbiol. 2022;60(12):1178-1190. Published online November 24, 2022; DOI: https://doi.org/10.1007/s12275-022-2416-1

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12 Citations

Abstract: Microbiome research has been on the rise recently for a more in-depth understanding of gout. Meanwhile, there is a need to understand the gut microbiome related to uric acid-lowering drug resistance. In this study, 16S rRNA gene-based microbiota analysis was performed for a total of 65 stool samples from 17 healthy controls and 48 febuxostat-treated gout patients (including 28 controlled subjects with decreased uric acid levels and 20 uncontrolled subjects with non-reduced uric acid levels). Alpha diversity of bacterial community decreased in the healthy control, controlled, and uncontrolled groups. In the case of beta diversity, the bacterial community was significantly different among groups (healthy control, controlled, and uncontrolled groups). Taxonomic biomarker analysis revealed the increased population of g-Bifidobacterium in healthy controls and g-Prevotella in uncontrolled patients. PCR further confirmed this result at the species level. Additionally, functional metagenomics predictions led to the exploration of various functional biomarkers, including purine metabolism. The results of this study can serve as a basis for developing potential new strategies for diagnosing and treating gout from microbiome prospects.

Pat- and Pta-mediated protein acetylation is required for horizontallyacquired virulence gene expression in Salmonella Typhimurium: Hyojeong Koo , Eunna Choi , Shinae Park , Eun-Jin Lee , Jung-Shin Lee; J. Microbiol. 2022;60(8):823-831. Published online May 27, 2022; DOI: https://doi.org/10.1007/s12275-022-2095-y

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Abstract: Salmonella Typhimurium is a Gram-negative facultative pathogen that causes a range of diseases, from mild gastroenteritis to severe systemic infection in a variety of animal hosts. S. Typhimurium regulates virulence gene expression by a silencing mechanism using nucleoid-associated proteins such as Histone-like Nucleoid Structuring protein (H-NS) silencing. We hypothesize that the posttranslational modification, specifically protein acetylation, of proteins in gene silencing systems could affect the pathogenic gene expression of S. Typhimurium. Therefore, we created acetylation-deficient mutant by deleting two genes, pat and pta, which are involved in the protein acetylation pathway. We observed that the pat and pta deletion attenuates mouse virulence and also decreases Salmonella’s replication within macrophages. In addition, the Δpat Δpta strain showed a decreased expression of the horizontally-acquired virulence genes, mgtC, pagC, and ugtL, which are highly expressed in low Mg2+. The decreased virulence gene expression is possibly due to higher H-NS occupancy to those promoters because the pat and pta deletion increases H-NS occupancy whereas the same mutation decreases occupancy of RNA polymerase. Our results suggest that Pat- and Pta-mediated protein acetylation system promotes the expression of virulence genes by regulating the binding affinity of H-NS in S. Typhimurium.

Availability of polyamines affects virulence and survival of Neisseria meningitidis: Poonam Kanojiya , Riya Joshi , Sunil D. Saroj; J. Microbiol. 2022;60(6):640-648. Published online April 18, 2022; DOI: https://doi.org/10.1007/s12275-022-1589-y

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4 Citations

Abstract: Neisseria meningitidis is a Gram-negative human-restricted pathogen that asymptomatically resides in the human respiratory tract. Meningococcal meningitis and sepsis both are caused by N. meningitidis. The bacterium must adhere to host epithelial cells in order to colonize effectively. The factors that determine the initial attachment to the host and dispersal, are not well understood. Metabolites released by the host may aid in meningococcal colonization and dissemination. Polyamines are aliphatic polycations that assist in cell survival and proliferation. The virulence properties of N. meningitidis after exposure to polyamines were investigated. Adhesion to nasopharyngeal epithelial cells increased in the presence of spermine. Also, the relative expression of adhesin, pilE increased in the presence of spermine. Further, relative expression of ctrA, ctrB and lipB was upregulated in the presence of spermidine, indicating increased capsule formation. Upregulated capsule synthesis of N. meningitidis in the presence of spermidine allows it to survive in murine macrophages. The study suggests the importance of the extracellular pool of polyamines in promoting virulence in N. meningitidis.

Prevalence and characteristics of the mcr-1 gene in retail meat samples in Zhejiang Province, China: Biao Tang , Jiang Chang , Yi Luo , Han Jiang , Canying Liu , Xingning Xiao , Xiaofeng Ji , Hua Yang; J. Microbiol. 2022;60(6):610-619. Published online March 31, 2022; DOI: https://doi.org/10.1007/s12275-022-1597-y

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10 Citations

Abstract: Considering the serious threat to food safety and public health posed by pathogens with colistin resistance, colistin was banned as a growth promoter in 2017 in China. In recent years, the resistance rate of Escherichia coli isolated from animal intestines or feces to colistin has decreased. However, the prevalence and characteristics of the mcr-1 gene in retail meat have not been well explored. Herein, 106 mcr-1-negative and 16 mcr- 1-positive E. coli isolates were randomly recovered from 120 retail meat samples and screened using colistin. The 106 E. coli isolates showed maximum resistance to sulfafurazole (73.58%) and tetracycline (62.26%) but susceptibility to colistin (0.00%). All 16 mcr-1-positive E. coli isolates showed resistance to colistin, were extended spectrum beta-lactamase (ESBL)-positive and exhibited complex multidrug resistance (MDR). For these 16 isolates, 17 plasmid replicons and 42 antibiotic resistance genes were identified, and at least 7 antibiotic resistance genes were found in each isolate. Acquired disinfectant resistance genes were identified in 75.00% (12/16) of the isolates. Furthermore, comparative genomic and phylogenetic analysis
results
indicated that these 16 mcr-1-positive E. coli isolates and the most prevalent mcr-1-harboring IncI2 plasmid in this study were closely related to other previously reported mcr-1-positive E. coli isolates and the IncI2 plasmid, respectively, showing their wide distribution. Taken together, our findings showed that retail meat products were a crucial reservoir of mcr-1 during the colistin ban period and should be continuously monitored.

Exploiting the antibacterial mechanism of phenazine substances from Lysobacter antibioticus 13-6 against Xanthomonas oryzae pv. oryzicola: Qi Liu , Jun Yang , Waqar Ahmed , Xiaoyan Wan , Lanfang Wei , Guanghai Ji; J. Microbiol. 2022;60(5):496-510. Published online March 31, 2022; DOI: https://doi.org/10.1007/s12275-022-1542-0

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13 Citations

Abstract: Bacterial leaf streak caused by Xanthomonas oryzae pv. oryzicola (Xoc) is one of the most destructive diseases affecting rice production worldwide. In this study, we extracted and purified phenazine substances from the secondary metabolites of Lysobacter antibioticus 13-6. The bacteriostatic mechanism of phenazine substances against Xoc was investigated through physiological response and transcriptomic analysis.
Results
showed that phenazine substances affects the cell membrane permeability of Xoc, which causes cell swelling and deformation, blockage of flagellum synthesis, and imbalance of intracellular environment. The changes in intracellular environment affect the physiological and metabolic functions of Xoc, which reduces the formation of pathogenic factors and pathogenicity. Through transcriptomic analysis, we found that among differentially expressed genes, the expression of 595 genes was induced significantly (275 up-regulated and 320 down-regulated). In addition, we observed that phenazine substances affects three main functions of Xoc, i.e., transmembrane transporter activity, DNA-mediated transposition, and structural molecular activity. Phenazine substances also inhibits the potassium ion transport system that reduces Xoc resistance and induces the phosphate ion transport system to maintain the stability of the internal environment. Finally, we conclude that phenazine substances could retard cell growth and reduce the pathogenicity of Xoc by affecting cell structure and physiological metabolism. Altogether, our study highlights latest insights into the antibacterial mechanism of phenazine substances against Xoc and provides basic guidance to manage the incidence of bacterial leaf streak of rice.

Potato tillage method is associated with soil microbial communities, soil chemical properties, and potato yield: Haiyan Ma , Chen Xie , Shunlin Zheng , Peihua Li , Hafsa Nazir Cheema , Jing Gong , Zhuqing Xiang , Juanjuan Liu , Jiahao Qin; J. Microbiol. 2022;60(2):156-166. Published online January 7, 2022; DOI: https://doi.org/10.1007/s12275-022-1060-0

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6 Citations

Abstract: Intensive potato continuous cropping (IPCC) results in low potato yields compared with non-intensive potato continuous cropping (PCC) and potato-maize rotation (PMRC). However, it is still unclear whether the degree of potato continuous cropping obstacle is related to the soil environment formed by the previous crop. To investigate the effect of planting potatoes and planting maize after harvesting the spring potatoes on soil chemical properties and soil microbial community structure, an experiment was carried out in the same origin soil environment over a period of seven years: (a) PCC, i.e., spring planting; (b) IPCC, i.e., autumn and spring planting (IPCC); (c) PMRC, i.e., spring potatoes and summer maize (PMRC), and (d) fallow (CK). We confirmed that the potato yield under PMRC was significantly higher than that under PCC and IPCC. Under IPCC, soil total phosphorus content was significantly higher than other treatments, whereas ammonium nitrogen content was the lowest. Compared with PCC and IPCC, PMRC had a higher ammonium nitrogen content and lower total phosphorus content. The significantly different fungal taxa in IPCC (Glomerellales, Plectosphaerella, Thelebolales) may threaten the health of the plant and positive correlated with soil total phosphorus, while other microbial taxa in PMRC (Bacillales, Polythrincium, Helotiales) can mainly promotes plant nitrogen uptake and protects plants against diseases. The PMRC-promoting taxa were positively correlated with the ammonium nitrogen content and negative correlated with soil total phosphorus content. In summary, the cropping systems might have affected potato yields by changed soil microorganism community structures – especially fungal community structures – and by the chemical properties of the soils that also depends on microbes.

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