Diversity of culturable root-associated/endophytic bacteria and their chitinolytic and aflatoxin inhibition activity of peanut plant in China

Abstract

A total of 72 isolates of root-associated/endophytic (RAE) bacteria were isolated from peanut plants grown in the main producing areas of 6 provinces in China. The 16S rRNA gene sequences of these isolates were determined and phylogenetic analyses revealed that 72 isolates belonged to the classes Bacilli (49 isolates) and Gammaproteobacteria (23 isolates). The majority of RAE bacteria in Bacilli belonged to 2 genera, Bacillus and Lysinibacillus (48 and 1) while those in Gammaproteobacteria belonged to the genera Enterobacter, Serratia, Stenotrophomonas, and Pseudomonas (7, 11, 3 and 2 isolates, respectively). This is the first report of Lysinibacillus xylanilyticus isolate as biocontrol agent against AFs. All of the selected RAE bacteria showed inhibitory activities against Aspergillus parasiticus (A. parasiticus) growth and/or aflatoxins (AFs) production by visual agar plate assay and tip culture method. Most of the RAE bacteria strains (96 % strains) were determined to have decreased mycelia growth or AFs production levels by >50 % (p < 0.05). Bacterial isolates were further characterized for chitinolytic activity and 22 strains (30 % strains) of identified RAE bacteria degraded colloidal chitin on the chitin medium plate. Ten selected chitinolytic RAE bacteria were tested for antifungal activity on peanuts and most of them significantly decreased mycelial growth and AFs production levels by >90 %. These results showed a wide distribution of biological control bacteria against AFs in Chinese peanut main producing areas and the selected RAE bacteria could potentially be utilized for the biocontrol of toxicogenic fungi.

Plant growth-promoting and phytopathogen-antagonistic properties of bacterial endophytes from potato (Solanum tuberosum L.) cropping systems

“…Field observations showed that the wilt fungus Verticillium dahliae, a major contributor to potato earlydying complex, was less prevalent in CONS soil management than in CONV management (F. J. Larney, personal communication). The disease control capabilities of endophytic bacteria have been reported in other studies on potato (Hong-Xian et al 2005;Pavlo et al 2011) and other crops (Sapak et al 2008;Wang et al 2013).…”

Characterization of an Alkali- and Halide-Resistant Laccase Expressed in E. coli: CotA from Bacillus clausii

“…In comparison, the newly reported alkali-stable laccases from actinomycetes [12] and Trametes sp. [11] had similar half-lifes (60 minutes) at only 60°C and pH 8, showing the substantial advantage of the characterized bacterial laccases over fungal orthologs if stability is preferred over redox potential. This advantage is, as shown in this work, further enhanced by the interplay of salt and pH at alkaline conditions where the cotA enzymes, in particular the cotA from B. clausii , work well.…”

The Aspergilli and Their Mycotoxins: Metabolic Interactions With Plants and the Soil Biota

“…Actinomycetes (e.g., Verheecke et al, 2014), Lactobacilli (e.g., Romanens et al, 2019), Bifidobacteria (e.g., Ghazvini et al, 2016), and Bacilli (Siahmoshteh et al, 2017) are the best-studied groups from these aspects. Several studies have conducted screening on microbial collections to find potential biocontrol isolates that inhibit mold growth, testing (1) bacteria ranging from endophytes and rhizosphere species (Wang et al, 2013); (2) traditional fermentation products (Ahlberg et al, 2017); (3) various other samples where natural interactions with toxigenic molds are far less plausible, as in halophilic soils (Jafari et al, 2018) or fish intestines (Veras et al, 2016). The effects on toxin production and the underlying mechanisms of growth and toxigenic nature are, similarly to yeasts, less understood and often not attempted to uncover.…”