The rhizospheres of traditional medicinal plants in Panxi, China, host a diverse selection of actinobacteria with antimicrobial properties

Abstract

Actinobacteria are a prolific source of antibiotics. Since the rate of discovery of novel antibiotics is decreasing, actinobacteria from unique environments need to be explored. In particular, actinobacterial biocontrol strains from medicinal plants need to be studied as they can be a source of potent antibiotics. We combined culture-dependent and culture-independent methods in analyzing the actinobacterial diversity in the rhizosphere of seven traditional medicinal plant species from Panxi, China, and assessed the antimicrobial activity of the isolates. Each of the plant species hosted a unique set of actinobacterial strains. Out of the 64 morphologically distinct isolates, half were Streptomyces sp., eight were Micromonospora sp., and the rest were members of 18 actinobacterial genera. In particular, Ainsliaea henryi Diels. hosted a diverse selection of actinobacteria, although the 16S ribosomal RNA (rRNA) sequence identity ranges of the isolates and of the 16S rRNA gene clone library were not congruent. In the clone library, 40% of the sequences were related to uncultured actinobacteria, emphasizing the need to develop isolation methods to assess the full potential of the actinobacteria. All Streptomyces isolates showed antimicrobial activity. While the antimicrobial activities of the rare actinobacteria were limited, the growth of Escherichia coli, Verticillium dahliae, and Fusarium oxysporum were inhibited only by rare actinobacteria, and strains related to Saccharopolyspora shandongensis and Streptosporangium roseum showed broad antimicrobial activity.

Analysis of Clostridium cluster I community diversity in pit mud used in manufacture of Chinese Luzhou-flavor liquor

“…Bands LZLJC2 and LZLJC4 were found in all pit mud samples, suggesting that C. ragsdalei, C. ljungdahlii, C. autoethanogenum, and C. kluyveri are the dominant species in pit mud. Compared with previous species identified in pit mud (2,8,10,14), pit mud samples in this study lacked C. sartagoforme, C. butyricum, C. perfringens, and C. cylindrosporum, possibly because some species were not sufficiently abundant for PCR amplification (33), or due to differences in application of PCR primers. Conversely, among species identified herein, C. kluyveri and C. ljungdahlii were previously identified.…”

Isolation and antimicrobial activities of actinobacteria closely associated with liquorice plants Glycyrrhiza glabra L. and Glycyrrhiza inflate BAT. in Xinjiang, China

“…However, since the production of antibiotics is strain-specific (Hotta & Okami, 1996), we cannot conclude if the antimicrobial activity of our S. niveus and S. humidus isolates was based on the aforementioned antibiotics. We isolated actinobacteria belonging to species that have shown antifungal activity: endophytic M. aurantiaca and rhizospheric S. luteoverticillatus include antifungal strains, and S. cyaneofuscatus has shown both in vivo and in vitro activity (Goudjal et al, 2014;Kim et al, 2012a;Zhao et al, 2012). The different antimicrobial ranges of the S. luteoverticillatus isolates from the rhizosphere of Stellera chamaejasme L. and from G. inflate was in accordance with the strain-specificity of antimicrobial activity.…”

“…The number of genera isolated is worth noting: 12 plant species in Amazonian rainforests in Peru and 26 medicinal plant species in Panxi, China, hosted two and six actinobacterial genera, respectively Bascom-Slack et al, 2009;Zhao et al, 2011), whereas here we isolated four genera from G. glabra alone. Isolation media play an important role in exploring culturable actinobacteria resources (Qin et al, 2009;Zhao et al, 2012). We employed four media to isolate a broad selection of actinobacteria.…”

“…To discover novel bioactive compounds, micro-organisms from unique environments and untapped sources should be explored (Maldonado et al, 2009;Mesbah et al, 2007;Strobel et al, 2004). Actinobacteria that produce a diverse range of secondary metabolites including various antibiotics are widely distributed in terrestrial and marine habitats (Jiang et al, 2007;Qin et al, 2009;Zhao et al, 2012). Endophytes are microorganisms that live inside plant tissues by symbiotic, parasitic or mutualistic means without causing immediately overt negative effects (Stone et al, 2000).…”

Diversity of bacteria and archaea in the rhizosphere of bioenergy crop Jatropha curcas

“…Actinobacteria has been found in rhizosphere of many plants, including cereal crops such as wheat (Zhao et al 2012; Mingma et al 2014). Streptomyces are major species of Actinobacteria , that are commonly found in roots of crops and terrestrial plants (Liu et al 2015).…”