Journal of Microbiology

Volume 53(9); September 2015

Review

MINIREVIEW] The cAMP/protein kinase A signaling pathway in pathogenic basidiomycete fungi: Connections with iron homeostasis: Jaehyuk Choi , Won Hee Jung , James W. Kronstad; J. Microbiol. 2015;53(9):579-587. Published online August 1, 2015; DOI: https://doi.org/10.1007/s12275-015-5247-5

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43 Citations

Abstract: A number of pathogenic species of basidiomycete fungi are either life-threatening pathogens of humans or major economic pests for crop production. Sensing the host is a key aspect of pathogen proliferation during disease, and signal transduction pathways are critically important for detecting environmental conditions and facilitating adaptation. This review focuses on the contributions of the cAMP/protein kinase A (PKA) signaling pathway in Cryptococcus neoformans, a species that causes meningitis in humans, and Ustilago maydis, a model phytopathogen that causes a smut disease on maize. Environmental sensing by the cAMP/PKA pathway regulates the production of key virulence traits in C. neoformans including the polysaccharide capsule and melanin. For U. maydis, the pathway controls the dimorphic transition from budding growth to the filamentous cell type required for proliferation in plant tissue. We discuss recent advances in identifying new components of the cAMP/PKA pathway in these pathogens and highlight an emerging theme that pathway signaling influences iron acquisition.

Research Support, Non-U.S. Gov'ts

Paenibacillus insulae sp. nov., isolated from soil: Sung-Jun Cho , Sung-Heun Cho , Tae-Su Kim , Suhk-Hwan Park , Seung-Bum Kim , Geon-Hyoung Lee; J. Microbiol. 2015;53(9):588-591. Published online August 27, 2015; DOI: https://doi.org/10.1007/s12275-015-4610-x

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Abstract: A Gram-stain-positive, motile, endospore-forming, and strictly aerobic rod-shaped bacterium designated DS80T was isolated from an island soil. The strain DS80T grew at temperatures between 15 and 40°C (optimum = 30°C) and at pH values ranging from 5.0 to 9.0 (optimum = 7.0). The phylogenetic analysis based on the comparisons of the 16S rRNA gene sequences showed that the isolate was affiliated to the genus Paenibacillus and was mostly related to Paenibacillus assamensis GPTSA11T (with the sequence similarity of 96.33%) and Paenibacillus urinalis 5402403T(95.48%). The G+C content of the genomic DNA was 44.0 mol% and the major fatty acids were anteiso-C15:0, iso-C15:0, iso-C16:0, and C16:1 ω11c. Strain DS80T contained MK-7 as the major menaquinone, and phosphatidylglycerol, phosphatidylethanolamine, and diphosphatidylglycerol as the major polar lipids. The peptidoglycan contained a major amount of meso-diaminopimelic acid. The chemotaxonomic profile of strain DS80T was consistent with that of Paenibacillus. However, the phenotypic properties clearly separated the strain from other species of the genus. Accordingly, a new species, Paenibacillus insulae sp. nov., is proposed (type strain =DS80T =JCM 17278T =KCTC 13833T).

Chujaibacter soli gen. nov., sp. nov., isolated from soil: Soo-Jin Kim , Jae-Hyung Ahn , Hang-Yeon Weon , Seung-Beom Hong , Soon-Ja Seok , Jeong-Seon Kim , Soon-Wo Kwon; J. Microbiol. 2015;53(9):592-597. Published online August 27, 2015; DOI: https://doi.org/10.1007/s12275-015-5136-y

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17 Citations

Abstract: A Gram-staining-negative, aerobic, non-flagellated, rod-shaped bacterial strain, KIS55-21T, was isolated from a soil sample from Chuja Island, Jeju Province, Republic of Korea. Strain KIS55-21T grew optimally at pH 7.0, at 28–30°C and in the presence of 0% (w/v) NaCl. Neighbor-joining and maximum-likelihood trees based on the 16S rRNA gene sequences revealed that strain KIS55-21T fell within the family Xanthomonadaceae and was closely related to Metallibacterium scheffleri DKET. Strain KIS55-21T exhibited the highest 16S rRNA gene sequence similarity (92.6%) to that of M. scheffleri DKET, with similarities of less than 92.0% to those of the genera Dokdonella, Rhodanobacter, Aquimonas, and Frateuria. Strain KIS55-21T contained ubiquinone-8 (Q-8) as the predominant ubiquinone, iso-C17:0, summed feature 9 (iso-C17:1 ω9c and/or C16:0 10-methyl), anteiso-C17:0 and C16:0 as the major fatty acids, and phosphatidylethanolamine, aminophospholipid, phosphatidylglycerol, diphosphatidylglycerol, and phosphatidylmonomethylethanolamine as the main polar lipids. The DNA G+C content of strain KIS55-21T was 65.9 mol%. Differential phenotypic and chemotaxonomic properties and phylogenetic data of strain KIS55-21T demonstrated that this strain is distinguishable from closely related genera within the family Xanthomonadaceae. On the basis of the data presented, strain KIS55-21T is considered to represent a novel genus and species, for which the name Chujaibacter soli gen. nov., sp. nov. is proposed. The type strain is KIS55-21T (=KACC 16971T =DSM 28578T).

Characterization of bacterial diversity associated with deep sea ferromanganese nodules from the South China Sea: De-Chao Zhang , Yan-Xia Liu , Xin-Zheng Li; J. Microbiol. 2015;53(9):598-605. Published online August 27, 2015; DOI: https://doi.org/10.1007/s12275-015-5217-y

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14 Citations

Abstract: Deep sea ferromanganese (FeMn) nodules contain metallic mineral resources and have great economic potential. In this study, a combination of culture-dependent and culture-independent (16S rRNA genes clone library and pyrosequencing)
methods
was used to investigate the bacterial diversity in FeMn nodules from Jiaolong Seamount, the South China Sea. Eleven bacterial strains including some moderate thermophiles were isolated. The majority of strains belonged to the phylum Proteobacteria; one isolate belonged to the phylum Firmicutes. A total of 259 near full-length bacterial 16S rRNA gene sequences in a clone library and 67,079 valid reads obtained using pyrosequencing indicated that members of the Gammaproteobacteria dominated, with the most abundant bacterial genera being Pseudomonas and Alteromonas. Sequence analysis indicated the presence of many organisms whose closest relatives are known manganese oxidizers, iron reducers, hydrogen-oxidizing bacteria and methylotrophs. This is the first reported investigation of bacterial diversity associated with deep sea FeMn nodules from the South China Sea.

Transcriptional profiles of laccase genes in the brown rot fungus Postia placenta MAD-R-698: Hongde An , Dongsheng Wei , Tingting Xiao; J. Microbiol. 2015;53(9):606-615. Published online August 1, 2015; DOI: https://doi.org/10.1007/s12275-015-4705-4

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11 Citations

Abstract: One of the laccase isoforms in the brown rot fungus Postia placenta is thought to contribute to the production of hydroxyl radicals, which play an important role in lignocellulose degradation. However, the presence of at least two laccase isoforms in this fungus makes it difficult to understand the details of this mechanism. In this study, we systematically investigated the transcriptional patterns of two laccase genes, Pplcc1 and Pplcc2, by quantitative PCR (qPCR) to better understand the mechanism. The qPCR results showed that neither of the two genes was expressed constitutively throughout growth in liquid culture or during the degradation of a woody substrate. Transcription of Pplcc1 was upregulated under nitrogen depletion and in response to a high concentration of copper in liquid culture, and during the initial colonization of intact aspen wafer. However, it was subject to catabolite repression by a high concentration of glucose. Transcription of Pplcc2 was upregulated by stresses caused by ferulic acid, 2, 6-dimethylbenzoic acid, and ethanol, and under osmotic stress in liquid culture. However, the transcription of Pplcc2 was downregulated upon contact with the woody substrate in solid culture. These results indicate that Pplcc1 and Pplcc2 are differentially regulated in liquid and solid cultures. Pplcc1 seems to play the major role in producing hydroxyl radicals and Pplcc2 in the stress response during the degradation of a woody substrate.

Identification of Psk2, Skp1, and Tub4 as trans-acting factors for uORF-containing ROK1 mRNA in Saccharomyces cerevisiae: Soonmee Jeon , Suran Lim , Jeemin Ha , Jinmi Kim; J. Microbiol. 2015;53(9):616-622. Published online August 27, 2015; DOI: https://doi.org/10.1007/s12275-015-5389-5

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Abstract: Rok1, a DEAD-box RNA helicase, is involved in rRNA processing and the control of cell cycle progression in Saccharomyces cerevisiae. Rok1 protein expression is cell cycle-regulated, declining at G1/S and increasing at G2. The downregulation of Rok1 expression in G1/S phase is mediated by the inhibitory action of two upstream open reading frames (uORFs) in the ROK1 5􍿁-untranslated region (5􍿁UTR). We identified Psk2 (PAS kinase), Skp1 (kinetochore protein) and Tub4 (γ-tubulin protein) as ROK1 5􍿁UTR-interacting proteins using yeast three-hybrid system. A deletion analysis of PSK2 or inactivation of temperature-sensitive alleles of SKP1 and TUB4 revealed that Rok1 protein synthesis is repressed by Psk2 and Skp1. This repression appeared to be mediated through the ROK1 uORF1. In contrast, Tub4 plays a positive role in regulating Rok1 protein synthesis and likely after the uORF1-mediated inhibitory regulation. These results suggest that 5􍿁UTR-interacting proteins, identified using three hybrid screening, are important for uORF-mediated regulation of Rok1 protein expression.

D101 is critical for the function of AttJ, a repressor of quorum quenching system in Agrobacterium tumefaciens: Chao Wang , Chunlan Yan , Yong-Gui Gao , Lian-Hui Zhang; J. Microbiol. 2015;53(9):623-632. Published online August 1, 2015; DOI: https://doi.org/10.1007/s12275-015-5100-x

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Abstract: The quorum quenching system of Agrobacterium tumefaciens is specifically activated upon entering the stationary phase. Evidence has shown that this system includes two key components: the IclR-type transcriptional factor AttJ (also named as BlcR) and the AHL-lactonase AttM (also named as BlcC). At exponential phase, AttJ binds to the promoter region of attM and thus suppresses the expression of attM. At stationary phase, however, the small molecule SSA directly binds to AttJ and relieves its inhibition of AttJ and thereby triggers the expression of attM. While the regulation of AttM has been extensively investigated, little is known about the regulation of AttJ. In this study, we demonstrated the D101 amino acid of AttJ is essential for the AttJ function. In vitro, the variant protein of AttJD101H appeared to be readily aggregated. In vivo, the D101H mutation in AttJ entirely abolished the inhibitory activity of AttJ and overexpressed attM in A. tumefaciens A6. In addition, D101H mutation led to an overexpression of attJ, indicating an auto-regulatory mechanism for the attJ regulation. Put together, these findings demonstrate that D101 is an important amino acid for the transcription activity of AttJ and the transcription of attJ is regulated by a negative feedback loop. These results expand previous biochemical characterization of AttJ and provide new mechanistic insights into the regulation of quorum quenching in A. tumefaciens.

Roles of RpoS in Yersinia pseudotuberculosis stress survival, motility, biofilm formation and type VI secretion system expression: Jingyuan Guan , Xiao Xiao , Shengjuan Xu , Fen Gao , Jianbo Wang , Tietao Wang , Yunhong Song , Junfeng Pan , Xihui Shen , Yao Wang; J. Microbiol. 2015;53(9):633-642. Published online August 27, 2015; DOI: https://doi.org/10.1007/s12275-015-0099-6

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47 Citations

Abstract: RpoS (σS), the stationary phase/stress σ factor, controls the expression of a large number of genes involved in cellular responses to a variety of stresses. However, the role of RpoS appears to differ in different bacteria. While RpoS is an important regulator of flagellum biosynthesis, it is associated with biofilm development in Edwardsiella tarda. Biofilms are dense communities formed by bacteria and are important for microbe survival under unfavorable conditions. The type VI secretion system (T6SS) discovered recently is reportedly associated with several phenotypes, ranging from biofilm formation to stress sensing. For example, Vibrio anguillarum T6SS was proposed to serve as a sensor for extracytoplasmic signals and modulates RpoS expression and stress response. In this study, we investigated the physiological roles of RpoS in Yersinia pseudotuberculosis, including bacterial survival under stress conditions, flagella formation, biofilm development and T6SS expression. We found that RpoS is important in resistance to multiple stressors–including H2O2, acid, osmotic and heat shock–in Y. pseudotuberculosis. In addition, our study showed that RpoS not only modulates the expression of T6SS but also regulates flagellum formation by positively controlling the flagellar master regulatory gene flhDC, and affects the formation of biofilm on Caenorhabditis elegans by regulating the synthesis of exopolysaccharides. Taken together, these results show that RpoS plays a central role in cell fitness under several adverse conditions in Y. pseudotuberculosis.

Antibacterial potential of a small peptide from Bacillus sp. RPT-0001 and its capping for green synthesis of silver nanoparticles: Supriya Deepak Patil , Rajnikant Sharma , Tapas Bhattacharyya , Piyush Kumar , Manasi Gupta , Bhupinder Singh Chaddha , Naveen Kumar Navani , Ranjana Pathania; J. Microbiol. 2015;53(9):643-652. Published online August 1, 2015; DOI: https://doi.org/10.1007/s12275-015-4686-3

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13 Citations

Abstract: Infirmity and death from diseases caused by unsafe food are a continual hazard to communal health safety and socio-economic growth throughout the world. Chemical preservatives are associated with health hazards and toxicity issues. In the study reported here, 200 soil isolates from Western Himalayan region in India were screened for potential antibacterial activity against food-borne pathogens. This study led to the isolation of a bacterial strain belonging to the Genus Bacillus and was designated as RPT-0001. The associated antibacterial activity was sensitive to pronase E treatment. Bioassay-guided fractionation using reverse phase high performance liquid chromatography (RP-HPLC) led to isolation of the antibacterial peptide designated as RPT-0001. The molecular weight of RPT-0001 was determined by electro- spray ionization mass spectroscopy (ESI-MS) as 276.9 Da. RPT-0001 was inhibitory to both Gram-negative and Grampositive food-borne bacteria tested. The characteristics of RPT-0001 do not match with that of any other known antibacterial peptides produced by Bacillus sp. or related genera. Purified RPT-0001 was successfully used in synthesis of silver nanoparticles effective against food-borne pathogenic bacteria. The antibacterial peptide and silver nanoparticles synthesized utilizing it as a capping and reducing agent hold promising potential in food preservation, in packaging material and as a therapeutic agent in the treatment of foodborne infections.

Pregnancy - associated human listeriosis: Virulence and genotypic analysis of Listeria monocytogenes from clinical samples: Dharmendra Kumar Soni , Durg Vijai Singh , Suresh Kumar Dubey; J. Microbiol. 2015;53(9):653-660. Published online August 1, 2015; DOI: https://doi.org/10.1007/s12275-015-5243-9

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30 Citations

Abstract: Listeria monocytogenes, a life-threatening pathogen, poses severe risk during pregnancy, may cause abortion, fetal death or neonatal morbidity in terms of septicemia and meningitis. The present study aimed at characterizing L. monocytogenes isolated from pregnant women based on serotyping, antibiotic susceptibility, virulence genes, in vivo pathogenicity test and ERIC- and REP-PCR fingerprint analyses. The results revealed that out of 3700 human clinical samples, a total of 30 (0.81%) isolates [12 (0.80%) from placental bit (1500), 18 (0.81%) from vaginal swab (2200)] were positive for L. monocytogenes. All the isolates belonged to serogroup 4b, and were + ve for virulence genes tested i.e. inlA, inlC, inlJ, plcA, prfA, actA, hlyA, and iap. Based on the mice inoculation tests, 20 isolates showed 100% and 4 isolates 60% relative virulence while 6 isolates were non-pathogenic. Moreover, 2 and 10 isolates were resistant to ciprofloxacin and cefoxitin, respectively, while the rest susceptible to other antibiotics used in this study. ERIC- and REP-PCR collectively depicted that the isolates from placental bit and vaginal swab had distinct PCR fingerprints except a few isolates with identical patterns. This study demonstrates prevalence of pathogenic strains mostly resistant to cefoxitin and/or ciprofloxacin. The results indicate the importance of isolating and characterizing the pathogen from human clinical samples as the pre-requisite for accurate epidemiological investigations.

The effect of dietary bovine colostrum on respiratory syncytial virus infection and immune responses following the infection in the mouse: Mei Ling Xu , Hyoung Jin Kim , Ga Ram Wi , Hong-Jin Kim; J. Microbiol. 2015;53(9):661-666. Published online August 27, 2015; DOI: https://doi.org/10.1007/s12275-015-5353-4

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18 Citations

Abstract: Human respiratory syncytial virus (hRSV) is the most common cause of respiratory tract infection among young children because of immature T cell immunity of them against hRSV. CD8 T cells play a pivotal role in clearing hRSV and preventing subsequent infection. We examined the effects of dietary bovine colostrum on virus infection and CD8 T cell responses following hRSV infection in the mouse model. Mice received bovine colostrum for 14 days prior to hRSV challenge, and lung indexes (severity of symptom) and lung virus titers were analyzed. In addition, the activation of CD8 T cells in the bronchoalveolar lavage fluids (BALFs) of mice receiving bovine colostrum were compared with those in the BALFs of mice receiving phosphate-buffered saline (PBS) or ribavirin, post virus challenge. The severity of infection and lung virus titers were reduced in the mice receiving bovine colostrum, compared to those receiving PBS. Moreover CD8 T cell responses were selectively enhanced in the former. Our results suggest that dietary bovine colostrum exerts the effects to inhibit hRSV and ameliorate the symptom by hRSV infection, and enhances the CD8 T cell response during the hRSV infection.

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