Isolation and characterization of Bacillus subtilis strain 1-L-29, an endophytic bacteria from Camellia oleifera with antimicrobial activity and efficient plant-root colonization

Abstract

Endophytic bacteria, which are common in plant tissues, may help to control plant pathogens and enhance plant growth. Camellia oleifera, an oil-producing plant, is widely grown in warm, subtropical, hilly regions in China. However, C. oleifera is strongly negatively affected by C. oleifera anthracnose, which is caused by Colletetrichum fructicola. To find a suitable biocontrol agent for C. oleifera anthracnose, 41 endophytes were isolated from the stems, leaves, and roots of C. oleifera. Bacterial cultures were identified based on analyses of 16S rDNA sequences; most strains belonged to the genus Bacillus. The antagonistic effects of these strains on C. fructicola were tested in vitro. In total, 16 strains inhibited C. fructicola growth, with B. subtilis strain 1-L-29 being the most efficient. Strain 1-L-29 demonstrated antagonistic activity against C. siamense, C. asianum, Fusarium proliferatum, Agaricodochium camellia, and Pseudomonas syringae. In addition, this strain produced indole acetic acid, solubilized phosphate, grew on N-free media, and produced siderophores. To facilitate further microecological studies of this strain, a rifampicin-resistant, green fluorescent protein (GFP)-labeled strain, 1-L-29gfp r , was created using protoplast transformation. This plasmid had good segregational stability. Strain 1-L-29gfp r was reintroduced into C. oleifera and successfully colonized root, stem, and leaf tissues. This strain remained at a stable concentration in the root more than 20 d after inoculation. Fluorescence microscopic analysis showed that strain 1-L-29gfp r thoroughly colonized the root surfaces of C. fructicola as well as the root vascular tissues of Arabidopsis thaliana.

Biological Control of Verticillium Wilt on Olive Trees by the Salt-Tolerant Strain Bacillus velezensis XT1

“…Rifampicin resistance is commonly used as a reliable marker to study plant colonization by Bacillus spp. and other soil bacteria [80][81][82][83][84]. Despite the fact that pleiotropic effects have recently been observed in a Bacillus velezensis rifampicin-resistant mutant strain [85], population dynamics of wild-type and antibiotic-resistant derivatives were observed to be similar in other Bacillus species [82].…”

Endophytic Bacillus subtilis P10 from Prunus cerasifera as a biocontrol agent against tomato Verticillium wilt

“…Citri (Huang et al, 2012), tomato bacterial wilt caused by Ralstonia solanacearum (Chen et al, 2013), and melon bacterial fruit blotch caused by Acidovorax citrulli (Fan et al, 2017). B. subtilis strains are the dominant endophytic bacteria associated with many plant species, and they commonly exhibit the ability to enhance host plant resistance to pathogenic fungi and bacteria (Ansary et al, 2018;Kushwaha et al, 2020;Xu et al, 2019Xu et al, , 2020. These B. subtilis also do not pose a risk to humans, making them ideal for use in biocontrol applications (Earl et al, 2008).…”

Genetic Diversity of Endophytic Bacillus strains (101 and 201) Isolated from Native Neem (Azadirachta indica L.) Plants of West Malaysia

“…The isolation of endophytic bacteria was carried out according to the protocol given by Xu et al (2020) and Ferreira et al (2017). Explants (roots, leaves, nodes and internodes) of neem were used for the isolation of endophytic bacterial strains.…”

“…Surface sterilized explants were transferred at nutrient agar media plates (Xu et al 2020). After two days of incubation of plates at 37  C, the bacterial strains started growing on the nutrient agar medium from inoculated explants.…”

“…After two days of incubation of plates at 37  C, the bacterial strains started growing on the nutrient agar medium from inoculated explants. These endophytic bacterial strains were carefully replaced to another set of nutrient agar medium for pure culture isolation and further bacterial strain identification (Tiwari and Thakur, 2014;Xu et al 2020). The strains were examined for morphology via Gram staining.…”