Journal of Microbiology

Journal Article

β-1,3-Glucan/CR3/SYK pathway-dependent LC3B-II accumulation enhanced the fungicidal activity in human neutrophils: Ding Li , Changsen Bai , Qing Zhang , Zheng Li , Di Shao , Xichuan Li; J. Microbiol. 2019;57(4):263-270. Published online February 5, 2019; DOI: https://doi.org/10.1007/s12275-019-8298-1

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Abstract: Since molecular genotyping has been established for the Candida species, studies have found that a single Candida strain (endemic strain) can persist over a long period of time and results in the spread of nosocomial invasive candidiasis without general characteristics of horizontal transmissions. Our previous study also found the existence of endemic strains in a cancer center in Tianjin, China. In the current study, we performed further investigation on endemic and non-endemic Candida albicans strains, with the aim of explaining the higher morbidity of endemic strains. In an in vivo experiment, mice infected with endemic strains showed significantly shorter survival time and higher kidney fungal burdens compared to mice infected with non-endemic strains. In an in vitro experiment, the killing percentage of neutrophils to endemic strains was significantly lower than that to non-endemic strains, which is positively linked to the ratio of LC3B-II/I in neutrophils. An immunofluorescence assay showed more β-1,3-glucan exposure on the cell walls of nonendemic strains compared to endemic strains. After blocking the β-glucan receptor (CR3) or inhibiting downstream kinase (SYK) in neutrophils, the killing percent to C. albicans (regardless of endemic and non-endemic strains) and the ratio of LC3B-II/I of neutrophils were significantly decreased. These data suggested that the killing capability of neutrophils to C. albicans was monitored by β-1,3-glucan via CR3/SYK pathway-dependent LC3B-II accumulation and provided an explanation for the variable killing capability of neutrophils to different strains of C. albicans, which would be beneficial in improving infection control and therapeutic strategies for invasive candidiasis.

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

Transcriptional Regulation of fksA, a β-1,3-Glucan Synthase Gene, by the APSES Protein StuA during Aspergillus nidulans Development: Bum-Chan Park , Yun-Hee Park , Soohyun Yi , Yu Kyung Choi , Eun-Hye Kang , Hee-Moon Park; J. Microbiol. 2014;52(11):940-947. Published online October 31, 2014; DOI: https://doi.org/10.1007/s12275-014-4517-y

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Abstract: The temporal and spatial regulation of β-1,3-glucan synthesis plays an important role in morphogenesis during fungal growth and development. Northern blot analysis showed that the transcription of fksA, the gene encoding β-1,3-glucan synthase in Aspergillus nidulans, was cell-cycle-dependent and increased steadily over the duration of the vegetative period, but its overall expression during the asexual and sexual stages was fairly constant up until the time of transcription cessation. In an A. nidulans strain mutated in the eukaryotic bHLH-like APSES transcription factor stuA1, the transcriptional level of fksA, and consequently the content of alkali-insoluble cell wall β-glucan, significantly increased at the conidial chain formation and maturation stage. Electrophoretic mobility shift assays revealed that StuA was bound to StREs (StuA Response Elements) on the fksA promoter region. Promoter analysis with sGFP-fusion constructs also indicated the negative regulation of fksA expression by StuA, especially during asexual development. Taken together, these data suggest that StuA plays an important role in cell wall biogenesis during the development of A. nidulans, by controlling the transcription level of fksA.

Selection of a Streptomyces Strain Able to Produce Cell Wall Degrading Enzymes and Active against Sclerotinia sclerotiorum: Adriana Fróes , Andrew Macrae , Juliana Rosa , Marcella Franco , Rodrigo Souza , Rosângela Soares , Rosalie Coelho; J. Microbiol. 2012;50(5):798-806. Published online November 4, 2012; DOI: https://doi.org/10.1007/s12275-012-2060-2

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Abstract: Control of plant pathogen Sclerotinia sclerotiorum is an ongoing challenge because of its wide host range and the persistence of its sclerotia in soil. Fungicides are the most commonly used method to control this fungus but these can have ecotoxicity impacts. Chitinolytic Streptomyces strains isolated from Brazilian tropical soils were capable of inhibiting S. sclerotiorum growth in vitro, offering new possibilities for integrated pest management and biocontrol, with a new approach to dealing with an old problem. Strain Streptomyces sp. 80 was capable of irreversibly inhibiting fungal growth. Compared to other strains, its crude enzymes had the highest chitinolytic levels when measured at 25°C and strongly inhibited sclerotia from S. sclerotiorum. It produced four hydrolytic enzymes involved in fungal cell wall degradation when cultured in presence of the fungal mycelium. The best production, obtained after three days, was 0.75 U/ml for exochitinase, 0.9 U/ml for endochitinase, 0.16 U/ml for glucanase, and 1.78 U/ml for peptidase. Zymogram analysis confirmed two hydrolytic bands of chitinolytic activity with apparent molecular masses of 45.8 and 206.8 kDa. One glucanase activity with an apparent molecular mass of 55 kDa was also recorded, as well as seven bands of peptidase activity with apparent molecular masses ranging from 15.5 to 108.4 kDa. Differential interference contrast microscopy also showed alterations of hyphal morphology after co-culture. Streptomyces sp. 80 seems to be promising as a biocontrol agent against S. sclerotiorum, contributing to the development of new methods for controlling plant diseases and reducing the negative impact of using fungicides.

NOTE] Antifungal Activity of Extracellular Hydrolases Produced by Autolysing Aspergillus nidulans Cultures: Melinda Szilágyi , Fruzsina Anton , Katalin Forgács , Jae-Hyuk Yu , István Pócsi , Tamás Emri; J. Microbiol. 2012;50(5):849-854. Published online November 4, 2012; DOI: https://doi.org/10.1007/s12275-012-2001-0

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Abstract: Carbon-starving Aspergillus nidulans cultures produce high activities of versatile hydrolytic enzymes and, among these, ChiB endochitinase and EngA β-1,3-endoglucanase showed significant antifungal activity against various fungal species. Double deletion of engA and chiB diminished the antifungal activity of the fermentation broths and increased conidiogenesis and long-term viability of A. nidulans, but decreased the growth rate on culture media containing weak carbon sources. Production of ChiB and EngA can influence fungal communities either directly due to their antifungal properties or indirectly through their effects on vegetative growth. Our data suggest saprophytic fungi as promising future candidates to develop novel biocontrol technologies.

The role and characterization of β-1,3-glucanase in biocontrol of fusarium solani by pseudomonas stutzeri YPL-1: Lim, Ho Seong , Kim, Sang Dal; J. Microbiol. 1995;33(4):295-301.

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Abstract: An antifungal Pseudomonas stutzeri YPL-1 produced extracellular chitinase and β-1,3-glucanase that were key enzymes in the decomposition of fungal hyphal walls. These lytic extracellular enzymes markedly inhibited mycelial growth of the phytopathogenic fungus Fusarium solani. A chitinase from P. stutzeri YPL-1 inhibited fungal mycelial growth by 87%, whereas a β-1,3-glucanase from the bacterium inhibited growth by 53%. Furthermore, co-operative action of the enzymes synergistically inhibited 95% of the fungal growth. The lytic enzymes caused abnormal swelling and retreating on the fungal hyphal walls in a dual cultures. Scanning electron microscopy clearly showed hyphal degradation of F. solani in the regions interacting with P. stutzeri YPL-1. In an in vivo pot test, P. stutzeri YPL-1 proved to have biocontrol ability as a powerful agent in controlling plant disease. Planting of kidney bean (Phaseolus vulgaris L.) seedlings with the bacterial suspension in F. solani-infested soil significantly suppressed the development of fusarial root-rot. The characteristics of a crude preparation of β-1,3-glucanase produced from P. stutzeri YPL-1 were investigated. The bacterium detected after 2 hr of incubation. The enzyme had optimum temperature and pH of 40℃ and pH 5.5, respectively. The enzyme was stable in the pH range of 4.5 to 7.0 and at temperatures below 40℃, with a half-life of 40 min at 60℃.

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