Influence of water activity and temperature on conidial germination and mycelial growth of ochratoxigenic isolates ofAspergillus ochraceus on grape juice synthetic medium. Predictive models

We have found that the organic solvent-resistance of Alpha-chymotrypsin (Alpha-CT) is enhanced by adsorbing Alpha-CT onto bamboo charcoal powder (BCP), which is obtained by pyrolyzing bamboo waste under nitrogen atmosphere, and is markedly dependent on the thermodynamic water activity (aw) in organic solvents. When BCP-adsorbed　Alpha-CT was immersed in acetonitrile at an appropriate water activity, it effectively enhanced the transesterification of N-acetyl-L-tyrosine ethyl ester (N-Ac-Tyr-OEt) with n-butanol (BuOH) to produce N-acetyl-L-tyrosine butyl ester (N-Ac-Tyr-OBu), compared to the hydrolysis of N-Ac-Tyr-OEt with water to give N-acetyl-L-tyrosine (N-Ac-Tyr-OH). When the water activity was 0.28, the initial rate of transesterification catalyzed by BCP-adsorbed Alpha-CT was about sixty times greater than that catalyzed by free Alpha-CT. Regarding the reaction selectivity which is defined as a ratio of the initial rate of transesterification to that of hydrolysis, BCP-adsorbed α-CT was much superior to free Alpha-CT. The catalytic activity of BCP-adsorbed Alpha-CT was markedly dependent on the reaction temperature. Furthermore, concerning the thermal stability at 50 oC, the half-life of BCP-adsorbed Alpha-CT exhibited 3.8-fold, compared to that of free Alpha-CT.

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Bacterial Inhibition on Beauveria bassiana Contributes to Microbiota Stability in Delia antiqua

Frontiers in Microbiology ◽

10.3389/fmicb.2021.710800 ◽

2021 ◽

Vol 12 ◽

Author(s):

Fangyuan Zhou ◽

Yunxiao Gao ◽

Mei Liu ◽

Letian Xu ◽

Xiaoqing Wu ◽

...

Keyword(s):

Beauveria Bassiana ◽

Mycelial Growth ◽

Bacterial Species ◽

Management Strategies ◽

Underlying Mechanism ◽

Conidial Germination ◽

Delia Antiqua ◽

Bacterial Microbiota ◽

Fungal Microbiota ◽

Microbial Environment

Given the multiple roles of associated microbiota in improving animal host fitness in a microbial environment, increasing numbers of researchers have focused on how the associated microbiota keeps stable under complex environmental factors, especially some biological ones. Recent studies show that associated microbiota interacts with pathogenic microbes. However, whether and how the interaction would influence microbiota stability is limitedly investigated. Based on the interaction among Delia antiqua, its associated microbiota, and one pathogen Beauveria bassiana, the associated microbiota's response to the pathogen was determined in this study. Besides, the underlying mechanism for the response was also preliminarily investigated. Results showed that B. bassiana neither infect D. antiqua larvae nor did it colonize inside the associated microbiota, and both the bacterial and fungal microbiota kept stable during the interaction. Further experiments showed that bacterial microbiota almost completely inhibited conidial germination and mycelial growth of B. bassiana during its invasion, while fungal microbiota did not inhibit conidial germination and mycelial growth of B. bassiana. According to the above results, individual dominant bacterial species were isolated, and their inhibition on conidial germination and mycelial growth of B. bassiana was reconfirmed. Thus, these results indicated that bacterial instead of fungal microbiota blocked B. bassiana conidia and stabilized the associated microbiota of D. antiqua larvae during B. bassiana invasion. The findings deepened the understanding of the role of associated microbiota–pathogen microbe interaction in maintaining microbiota stability. They may also contribute to the development of novel biological control agents and pest management strategies.

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Saprophytic microorganisms with potential for biological control of Botrytis cinerea on Geraldton waxflower flowers

Australian Journal of Experimental Agriculture ◽

10.1071/ea00112 ◽

2001 ◽

Vol 41 (5) ◽

pp. 697 ◽

Cited By ~ 8

Author(s):

D. R. Beasley ◽

D. C. Joyce ◽

L. M. Coates ◽

A. H. Wearing

Keyword(s):

Botrytis Cinerea ◽

Mycelial Growth ◽

Germ Tube ◽

Conidial Germination ◽

Pseudomonas Sp ◽

Trichoderma Spp ◽

Fusarium Sp ◽

Flower Abscission ◽

Germ Tube Elongation

Saprophytic bacteria, yeasts and filamentous fungi were isolated from Geraldton waxflower flowers and screened to identify potential antagonism towards Botrytis cinerea. Isolates from other sources (e.g. avocado) were also tested. Isolates were initially screened in vitro for inhibition of B. cinerea conidial germination, germ tube elongation and mycelial growth. The most antagonistic bacteria, yeasts and fungi were selected for further testing on detached waxflower flowers. Conidia of the pathogen were mixed with conidia or cells of the selected antagonists, co-inoculated onto waxflower flowers, and the flowers were sealed in glass jars and incubated at 20˚C. The number of days required for the pathogen to cause flower abscission was determined. The most antagonistic bacterial isolate, Pseudomonas sp. 677, significantly reduced conidial germination and retarded germ tube elongation of B. cinerea. None of the yeast or fungal isolates tested was found to significantly reduce conidial germination or retard germ tube elongation, but several significantly inhibited growth of B. cinerea. Fusarium sp., Epicoccum sp. and Trichoderma spp. were the most antagonistic of these isolates. Of the isolates tested on waxflower, Pseudomonas sp. 677 was highly antagonistic towards B. cinerea and delayed waxflower abscission by about 3 days. Trichoderma harzianum also significantly delayed flower abscission. However, as with most of the fungal antagonists used, inoculation of waxflower flowers with this isolate resulted in unsightly mycelial growth.

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