Bryophytes Harbor Cultivable Actinobacteria With Plant Growth Promoting Potential

Abstract

This study was designed to investigate the cultivable actinobacteria associated with bryophytes and their plant growth promoting ability. Thirteen actinobacteria were isolated and tested for their ability to promote growth of plant in vitro and in planta . All isolates were able to produce IAA and siderophores. Six isolates were identified as members of the genus Micromonospora . Five isolates belonged to the genus Streptomyces and one each of Microbispora and Mycobacterium . Micromonospora sp. CMU55-4 was inoculated to rare moss [ Physcomitrium sphaericum (C. Ludw.) Fürnr.] and could increase the amount of carotenoid, fresh weight, and dry weight of this moss. In addition, this strain promoted capsule production, and rescued P. sphaericum ’s gametophytes during acclimatization to land. Strain CMU55-4 was identified as Micromonospora chalcea based on whole genome sequence analysis. Its plant growth promoting potential was further characterized through genome mining. The draft genome size was 6.6 Mb (73% GC). The genome contained 5,933 coding sequences. Functional annotation predicted encoded genes essential for siderophore production, phosphate solubilization that enable bacteria to survive under nutrient limited environment. Glycine-betaine accumulation and trehalose biosynthesis also aid plants under drought stress. M. chalcea CMU55-4 also exhibited genes for various carbohydrate metabolic pathways indicating those for efficient utilization of carbohydrates inside plant cells. Additionally, predictive genes for heat shock proteins, cold shock proteins, and oxidative stress such as glutathione biosynthesis were identified. In conclusion, our results demonstrate that bryophytes harbor plant growth promoting actinobacteria. A representative isolate, M. chalcea CMU55-4 promotes the growth of P. sphaericum moss and contains protein coding sequences related to plant growth promoting activities in its genome.

A Comparative Analysis of the Microbiome of Kiwifruit at Harvest Under Open-Field and Rain-Shelter Cultivation Systems

“…The phyla, Proteobacteria, Actinobacteria, Bacteroidetes, and Firmicutes have been reported to be widely distributed on the fruit surface of plant species, and contain a variety of taxa with different ecological roles, functioning as antagonists, symbionts (especially endophytes), and saprophytes ( Insuk et al, 2020 ; Lee et al, 2020 ; Mamphogoro et al, 2020 ). Actinobacteria have been reported to have a higher abundance in the endophytic community of kiwifruit cultivars that are more resistant to bacterial canker ( Cho et al, 2018 ).…”

“…Actinobacteria have been reported to have a higher abundance in the endophytic community of kiwifruit cultivars that are more resistant to bacterial canker ( Cho et al, 2018 ). Insuk et al (2020) assessed the in vitro and in vivo growth- promoting activity of 13 strains of Actinomycetes isolated from bryophytes. They found that all of the tested isolates produced IAA and also sequestered iron, which promoted the growth of bryophytes.…”

“…Several epiphytic bacterial species isolated from the phyllosphere have been reported to be strong competitors against plant pathogens, thus acting as BCAs ( Enya et al, 2007 ; Sartori et al, 2017 ). They can secrete antimicrobial substances ( Insuk et al, 2020 ; López et al, 2020 ), compete for nutrients and space in a limited space, or interfere with the signaling systems of pathogens ( Volksch and May, 2001 ). Dong et al (2021) studied the epiphytic and endophytic fungal communities of tomato plant roots, leaves, fruits, and seeds.…”

Taxonomic and Metabolite Diversities of Moss-Associated Actinobacteria from Thailand

“…The investigation of actinobacteria from lower plants, such as bryophytes (including mosses), and their beneficial traits are still rare. Recently, a member of the actinobacteria genus Micromonospora was reported from bryophytes, which showed plant growth-promoting activity in vitro and in planta [12]. Such a result suggests a potentially important role of actinobacteria in mosses.…”

“…They play important roles in food web dynamics, carbon and nutrient cycling, and soil temperature and moisture regulations [14]. Previous research has shown that moss-associated microbes are capable of enhancing the growth of the moss Physcomitrium sphaericum during its acclimatization from the laboratory environment to natural field soil [12], fix N 2 in the air [15], and contribute to the process of biomass decomposition [16].…”