Journal of Microbiology

Volume 56(2); February 2018

Journal Articles

A common evolutionary pathway for maintaining quorum sensing in Pseudomonas aeruginosa: Bai-min Lai , Hui-cong Yan , Mei-zhen Wang , Na Li , Dong-sheng Shen; J. Microbiol. 2018;56(2):83-89. Published online February 2, 2018; DOI: https://doi.org/10.1007/s12275-018-7286-1

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Abstract: In the bacterium Pseudomonas aeruginosa, the synthesis and secretion of extracellular protease is a typical cooperative behavior regulated by quorum sensing. However, this type of cooperative behavior is easily exploited by other individuals who do not synthesize public goods, which is known as the “tragedy of the commons”. Here P. aeruginosa was inoculated into casein media with different nitrogen salts added. In casein broth, protease (a type of public good) is necessary for bacterial growth. After 30 days of sequential transfer, some groups propagated stably and avoided “tragedy of the commons”. The evolved cooperators who continued to synthesize protease were isolated from these stable groups. By comparing the characteristics of quorum sensing in these cooperators, an identical evolutionary pattern was found. A variety of cooperative behaviors regulated by quorum sensing, such as the synthesis and secretion of protease and signals, were significantly reduced during the process of evolution. Such reductions improved the efficiency of cooperation, helping to prevent cheating. In addition, the production of pyocyanin, which is regulated by the RhlIR system, increased during the process of evolution, possibly due to its role in stabilizing the cooperation. This study contributes towards our understanding of the evolution of quorum sensing of P. aeruginosa.

Spirosoma pomorum sp. nov., isolated from apple orchard soil: Weilan Li , Seung-Yeol Lee , In-Kyu Kang , Leonid N. Ten , Hee-Young Jung; J. Microbiol. 2018;56(2):90-96. Published online February 2, 2018; DOI: https://doi.org/10.1007/s12275-018-7430-y

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Abstract: A Gram-negative, motile, rod-shaped, aerobic bacterial strain, designated S7-2-11T, was isolated from apple orchard soil from Gyeongsangnam-do Province, Republic of Korea, and was characterized taxonomically using a polyphasic approach. 16S rRNA gene sequence analysis indicated that strain S7-2- 11T belongs to the family Cytophagaceae in phylum Bacteroidetes, and is closely related to Spirosoma luteolum 16F6ET (94.2% identity), Spirosoma knui 15J8-12T (92.7%), and Spirosoma linguale DSM 74T (91.0%). The G + C content of the genomic DNA of strain S7-2-11T was 49.8 mol%. Strain S7-2-11T contained summed feature 3 (C16:1 ω7c/C16:1 ω6c; 35.1%), C16:1 ω5c (22.4%), C15:0 iso (13.9%), and C17:0 iso 3-OH (10.6%) as major cellular fatty acids, and MK-7 as the predominant respiratory quinone. The main polar lipids were phosphatidylethanolamine, an unidentified aminophospholipid, and two unidentified polar lipids. Phenotypic and chemotaxonomic data supported the affiliation of strain S7-2-11T with the genus Spirosoma. The results of physiological and biochemical tests showed the genotypic and phenotypic differentiation of the isolate from recognized Spirosoma species. On the basis of its phenotypic properties, genotypic distinctiveness, and chemotaxonomic features, strain S7-2-11T represents a novel species of the genus Spirosoma, for which the name Spirosoma pomorum sp. nov. is proposed. The type strain is S7-2-11T (= KCTC 52726T = JCM 32130T).

Lysobacter spongiae sp. nov., isolated from spongin: Heejae Choi , Wan-Taek Im , Jin-Sook Park; J. Microbiol. 2018;56(2):97-103. Published online February 2, 2018; DOI: https://doi.org/10.1007/s12275-018-7462-3

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Abstract: A Gram-negative, motile, aerobic and rod-shaped bacterial strain designated 119BY6-57T was isolated from spongin. The taxonomic position of the novel isolate was confirmed using the polyphasic approach. Strain 119BY6-57T grew well at 25– 30°C on marine agar. On the basis of 16S rRNA gene sequence similarity, strain 119BY6-57T belongs to the family Xanthomonadaceae and is related to Lysobacter aestuarii S2-CT (99.8% sequence similarity), L. maris KMU-14T (97.5%), and L. daejeonensis GH1-9T (97.3%). Lower sequence similarities (97.0%) were found with all of the other recognized members of the genus Lysobacter. The G + C content of the genomic DNA was 69.9 mol%. The major respiratory quinone was Q-8 and the major fatty acids were C16:0 iso, C15:0 iso, summed feature 9 (comprising C17􍾙:1 iso ω9c and/or C16:0 10-methyl), summed feature 3 (comprising C16􍾙:1 ω7c and/or C16:1 ω6c), and C11:0 iso 3-OH. The polar lipids were phosphatidylglycerol, phosphatidylethanolamine, diphosphatidylglycerol, three unidentified phospholipids, and an unidentified polar lipid. DNADNA relatedness values between strain 119BY6-57T and its closest phylogenetically neighbors were below 48.0 ± 2.1%. Based on genotypic and phenotypic characteristics, it is concluded that strain 119BY6-57T is a new member within the genus Lysobacter, for which the name Lysobacter spongiae sp. nov. is proposed. The type strain is 119BY6-57T (= KACC 19276T = LMG 30077T).

Contrasting patterns of the bacterial and archaeal communities in a high-elevation river in northwestern China: Yang Hu , Jian Cai , Chengrong Bai , Keqiang Shao , Xiangming Tang , Guang Gao; J. Microbiol. 2018;56(2):104-112. Published online February 2, 2018; DOI: https://doi.org/10.1007/s12275-018-7244-y

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Abstract: The patterns of macrobiota in lotic ecosystems have been extensively explored, however, the dynamics of microbiota remain poorly investigated, especially in the high-elevation region. To address this deficit, we collected eight samples to unveil the bacterial and archaeal community in the Kaidu river, located at the arid region of northwestern China (an average of 2,500 m a.s.l.). For the bacterial community, phylogenetically Betaproteobacteria prevailed, followed by Alphaproteobacteria and Actinobacteria; at the finer genus level, Limnohabitans and Variovorax were prominent. Along the river, the bacterial community showed a continuous succession. Specifically, their α- and β-diversity gradually increased, suggesting a distance-decay pattern. Additionally, there was an ecological transition between the dominant and the rare sub-community along the river: the relative abundance of the dominant members gradually decreased as the rare members increased. We report that temperature and spatial distance were significantly related to the variation of bacterial community. Variance partitioning analysis showed that the environmental factors contributed more to the bacterial community than did the spatial distance. In the case of the archaeal community, the methanogenic groups, mainly Methanosaeta and Methanosarcina, were prominent within the Kaidu river. Unlike the continuous change in the patterns of the bacterial community, the archaeal community showed a constant pattern along the river. Our results showed that the archaeal community was independent of the environmental and spatial factors. We propose that the inoculation of soil-derived archaea is responsible for the archaeal community in the Kaidu river. Together, our study demonstrated that the bacterial community in the high-elevation Kaidu river is a continuum, whereas the archaeal community is not.

Functional expression and enzymatic characterization of Lactobacillus plantarum cyclomaltodextrinase catalyzing novel acarbose hydrolysis: Myoung-Uoon Jang , Hye-Jeong Kang , Chang-Ku Jeong , Yewon Kang , Ji-Eun Park , Tae-Jip Kim; J. Microbiol. 2018;56(2):113-118. Published online February 2, 2018; DOI: https://doi.org/10.1007/s12275-018-7551-3

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Abstract: Cyclomaltodextrinases (CDases) belong to Glycoside Hydrolases (GH) family 13, which show versatile hydrolyzing and/or transglycosylation activity against cyclodextrin (CD), starch, and pullulan. Especially, some CDases have been reported to hydrolyze acarbose, a potent α-glucosidase inhibitor, and transfer the resulting acarviosine-glucose to various acceptors. In this study, a novel CDase (LPCD) gene was cloned from Lactobacillus plantarum WCFS1, which encodes 574 amino acids (64.6 kDa) and shares less than 44% of identities with the known CDase-family enzymes. Recombinant LPCD with C-terminal six-histidines was produced and purified from Escherichia coli. It showed the highest activity on β-CD at 45°C and pH 5.0, respectively. Gel permeation chromatography analysis revealed that LPCD exists as a dodecameric form (~826 kDa). Its hydrolyzing activity on β- CD is almost same as that on starch, whereas it can hardly attack pullulan. Most interestingly, LPCD catalyzed the unique modes of action in acarbose hydrolysis to produce maltose and acarviosine, as well as to glucose and acarviosineglucose.

Isolation and characterization of Aspergillus flavus strains in China: Firew Tafesse Mamo , Bo Shang , Jonathan Nimal Selvaraj , Yan Wang , Yang Liu; J. Microbiol. 2018;56(2):119-127. Published online February 2, 2018; DOI: https://doi.org/10.1007/s12275-018-7144-1

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Abstract: Important staple foods (peanuts, maize and rice) are susceptible to contamination by aflatoxin (AF)-producing fungi such as Aspergillus flavus. The objective of this study was to explore non-aflatoxin-producing (atoxigenic) A. flavus strains as biocontrol agents for the control of AFs. In the current study, a total of 724 A. flavus strains were isolated from different regions of China. Polyphasic approaches were utilized for species identification. Non-aflatoxin and non-cyclopiazonic acid (CPA)-producing strains were further screened for aflatoxin B1 (AFB1) biosynthesis pathway gene clusters using a PCR assay. Strains lacking an amplicon for the regulatory gene aflR were then analyzed for the presence of the other 28 biosynthetic genes. Only 229 (32%) of the A. flavus strains were found to be atoxigenic. Smaller (S) sclerotial phenotypes were dominant (51%) compared to large (L, 34%) and non-sclerotial (NS, 15%) phenotypes. Among the atoxigenic strains, 24 strains were PCR-negative for the fas-1 and aflJ genes. Sixteen (67%) atoxigenic A. flavus strains were PCRnegative for 10 or more of the biosynthetic genes. Altogether, 18 new PCR product patterns were observed, indicating great diversity in the AFB1 biosynthesis pathway. The current study demonstrates that many atoxigenic A. flavus strains can be isolated from different regions of China. In the future laboratory as well as field based studies are recommended to test these atoxigenic strains as biocontrol agents for aflatoxin contamination.

The antimicrobial potential of a new derivative of cathelicidin from Bungarus fasciatus against methicillin-resistant Staphylococcus aureus: Mercedeh Tajbakhsh , Abdollah Karimi , Abolghasem Tohidpour , Naser Abbasi , Fatemeh Fallah , Maziar Mohammad Akhavan; J. Microbiol. 2018;56(2):128-137. Published online February 2, 2018; DOI: https://doi.org/10.1007/s12275-018-7444-5

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Abstract: Cathelicidins are a family of antimicrobial peptides which exhibit broad antimicrobial activities against antibiotic-resistant bacteria. Considering the progressive antibiotic resistance, cathelicidin is a candidate for use as an alternative approach to treat and overcome the challenge of antimicrobial resistance. Cathelicidin-BF (Cath-BF) is a short antimicrobial peptide, which was originally extracted from the venom of Bungarus fasciatus. Recent studies have reported that Cath-BF and some related derivatives exert strong antimicrobial and weak hemolytic properties. This study investigates the bactericidal and cytotoxic effects of Cath-BF and its analogs (Cath-A and Cath-B). Cath-A and Cath-B were designed to increase their net positive charge, to have more activity against methicillin resistant S. aureus (MRSA). The results of this study show that Cath-A, with a +17-net charge, has the most noteworthy antimicrobial activity against MRSA strains, with minimum inhibitory concentration (MIC) ranging between 32–128 μg/ml. The bacterial kinetic analysis by 1 × MIC concentration of each peptide shows that Cath-A neutralizes the clinical MRSA isolate for 60 min. The present data support the notion that increasing the positive net charge of antimicrobial peptides can increase their potential antimicrobial activity. Cath-A also displayed the weakest cytotoxicity effect against human umbilical vein endothelial and H9c2 rat cardiomyoblast cell lines. Analysis of the hemolytic activity reveals that all three peptides exhibit minor hemolytic activity against human erythrocytes at concentrations up to 250 μg/ml. Altogether, these results suggest that Cath-A and Cath-B are competent candidates as novel antimicrobial compounds against MRSA and possibly other multidrug resistant bacteria.

Probiotic potential of novel Lactobacillus strains isolated from salted-fermented shrimp as antagonists for Vibrio parahaemolyticus: Bao Le , Seung Hwan Yang; J. Microbiol. 2018;56(2):138-144. Published online February 2, 2018; DOI: https://doi.org/10.1007/s12275-018-7407-x

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Abstract: Lactobacillus strains have been considered good candidates as biological control agents for prevention or treatment of plant and animal infections. One L. plantarum strain FB003 and three strains (FB011, FB081, and FB110) which closed to L. sakei were isolated from fermented and salted shrimp and their abilities in inhibiting growth of Vibrio parahaemolyticus were characterized. These strains were selected as potential probiotics based on their oro-gastro-intestinal resistance, gut colonization, adhesion to Caco-2 cells, antimicrobial activities, antibiotic resistance, and safety aspects.
Results
of this study revealed that these isolates possessed high aggregation activities against pathogens in host intestines. Strain FB011 strain showed higher coaggregation and immunomodulatory activity in the gastro-intestinal tract than L. plantarum. These difference effects of Lactobacillus strains provide valuable information about using them to prevent Vibrio infections in the aquaculture industry.

Effects of heat-killed Lactobacillus plantarum against influenza viruses in mice: Sehee Park , Jin Il Kim , Joon-Yong Bae , Kirim Yoo , Hyunung Kim , In-Ho Kim , Man-Seong Park , Ilseob Lee; J. Microbiol. 2018;56(2):145-149. Published online February 2, 2018; DOI: https://doi.org/10.1007/s12275-018-7411-1

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Abstract: The potential use of dietary measures to treat influenza can be an important alternative for those who lack access to influenza vaccines or antiviral drugs. Lactobacillus plantarum (Lp) is one of many lactic acid bacteria that grow in ‘kimchi’, an essential part of Korean meal, and several strains of Lp reportedly show protective effects against influenza. Using heat-killed Lp (nF1) isolated from kimchi, which is known for its immunomodulatory effects, we investigated whether regular oral intake of nF1 could influence the outcome of influenza virus infection in a mouse model. In a lethal challenge with influenza A (H1N1 and H3N2 subtypes) and influenza B (Yamagata lineage) viruses, daily oral administration of nF1 delayed the mean number of days to death of the infected mice and resulted in increased survival rates compared with those of the non-treated mice. Consistent with these observations, nF1 treatment also significantly reduced viral replication in the lungs of the infected mice. Taken together, our results might suggest the remedial potential of heatkilled Lactobacillus probiotics against influenza.

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