Journal of Microbiology

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

Effects of Fengycin from Bacillus subtilis fmbJ on Apoptosis and Necrosis in Rhizopus stolonifer: Qunyong Tang , Xiaomei Bie , Zhaoxin Lu , Fengxia Lv , Yang Tao , Xiaoxu Qu; J. Microbiol. 2014;52(8):675-680. Published online August 1, 2014; DOI: https://doi.org/10.1007/s12275-014-3605-3

Abstract: The lipopeptide antibiotic fengycin, produced by Bacillus subtilis, strongly inhibits growth of filamentous fungi. In this study, we evaluated the effects of fengycin treatment on apoptosis and necrosis in Rhizopus stolonifer by means of cell staining and epifluorescence microscopy. At fengycin concentrations less than 50 μg/ml, treated fungal cells demonstrated a dose-dependent increase in apoptosis-associated markers compared with the untreated control. These markers included chromatin condensation, reactive oxygen species accumulation, mitochondrial membrane potential depolarization, phosphatidylserine externalization, and the occurrence of DNA strand breaks. These results showed that fungal cells were impaired in a number of important functions and entered apoptosis upon treatment with low concentrations of fengycin. In contrast, high concentrations (>50 μg/ml) induced necrosis, indicating that the fungicidal action of fengycin operates via two modes: apoptosis at low concentrations and necrosis at high concentrations. Additionally, the apoptotic effect that we have shown suggests that lower concentrations of fengycin than previously thought may be effective for food preservation.

Molecular Cloning and Expression Analysis of a Delta 6-Fatty Acid Desaturase Gene from Rhizopus stolonifer Strain YF6 Which Can Accumulate High Levels of Gamma-Linolenic Acid: Xia Wan , Yinbo Zhang , Ping Wang , Mulan Jiang; J. Microbiol. 2011;49(1):151-154. Published online March 3, 2011; DOI: https://doi.org/10.1007/s12275-011-0254-7

Abstract: The delta 6-desaturase gene was cloned from Rhizopus stolonifer, which could accumulate up to 49% of gamma-linolenic acid (GLA, C18:3 Δ6,9,12) to the total fatty acids. The cloned DNA contains a 1,380 bp open reading frame encoding a protein of 460 amino acids, which showed high similarity to those of fungal delta 6-desaturases with three conserved histidine-rich motifs and HPGG motif. Notably, this deduced sequence had a shorter C-terminus. Results demonstrated that the cDNA sequence exhibited delta 6-desaturase activity by accumulation of about 22.4% of GLA to the total fatty acids in the recombinant Pichia pastoris strain GS115.

Antifungal Activity and Mechanism of Fengycin in the Presence and Absence of Commercial Surfactin Against Rhizopus stolonifer: Yang Tao , Xiao-mei Bie , Feng-xia Lv , Hai-zhen Zhao , Zhao-xin Lu; J. Microbiol. 2011;49(1):146-150. Published online March 3, 2011; DOI: https://doi.org/10.1007/s12275-011-0171-9

Abstract: The antifungal activity and mechanism of fengycin in the presence and absence of commercial surfactin against Rhizopus stolonifer were investigated. The MIC (minimal inhibitory concentration) of fengycin without commercial surfactin added was 0.4 mg/ml while the MIC of fengycin with commercial surfactin added was 2.0 mg/ml. Fengycin acted on cell membrane and cellular organs and inhibited DNA synthesis. The antifungal effect of fengycin was reduced after commercial surfactin was added. All these results suggest that the fungal cell membrane may be the primary target of fengycin action and commercial surfactin may reduce the antifungal activity of fengycin.

Microscopic Examination of the Suppressive Action of Antifungal Substances from Pseudomonas aeruginosa on Asexual Sporulation of Fungi: Yoon, Kwon S. , Min, Bu Y. , Choi, Hyoung T. , Lee, Jong K. , Kim, Kun W.; J. Microbiol. 1999;37(1):27-34.

Abstract: Two fractions with unusual antifungal activity that suppress asexual sporulation of several fungi were obtained from culture filtrate of Pseudomonas aeruginosa and were partially purified through the repeated silicagel flash column chromatographies. The sporulation-suppressive actions of these fractions in Aspergillus nidulans, Rhizopus stolonifer, and Coprinus cinereus, were analyzed by light and electron microscopes. The germination ability of the spores produced in the presence of these fractions were also checked to determine the persistent effects of these antifungal substances on the next generation. Light microscopic observation of developing sporangia of R. stolonifer grown in the presence of both fractions revealed that the significant number of sporangia failed to reach maturity, and frequently, uncontrolled growths of hyphae and rhizoids from the sporangiophores were found. In A. nidulans addition of these fractions appeared to cause different classes of morphological abnormality in conidia development, which included aborted formation of conidiogenous cells from the apex of conidiophores and enhanced hyphal growths either at the tip or middle of the conidiophores. Germination abilities of spores obtained from the cultures grown in the presence of antifungal fractions were 40∼60% in Aspergillus, 50∼80% in Coprinus (thallic spores), and 30∼40% in Rhizopus compared to those of normal spores.

PCR-DGGE and PCR-RFLP Analyses of the Internal Transcribed Spacer (ITS) of Ribosomal DNA in the Genus Rhizopus: You-Jung Park , Yong-Keel Choi , Byung-Re Min; J. Microbiol. 2003;41(2):157-160.

Abstract: To estimate genetic relationships within the genus Rhizopus, genetic variations in 20 strains were investigated by DGGE and PCR-RFLP of rDNA ITS region (ITS1, ITS2, 5.8S). The size of the amplified products showed the interspecific polymorphisms, 650 bp, 700 bp, and 900 bp. The DGGE approach allowed the separation of PCR amplicons of the same length according to their sequence variations. When the rDNA ITS region was digested with six restriction enzymes, 20 strains were classified into five RFLP haplotypes. The range of similarity between the 20 strains by PCR-RFLP was 42.3-100%. Based on the results of DGGE and PCR-RFLP, the 20 strains were divided into four groups, R. oryzae, R. stolonifer, R. microsporus and R. homothallicus. Further study of R. homothallicus is required.

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