Unraveling growth-promoting potential of plant beneficial actinobacteria on tropical bryophytes

Abstract

Bryophytes are non-vascular plants with dominant gametophyte stage that play vital ecological roles in natural ecosystems. Unfortunately, their populations are currently in decline due to habitat destruction and various anthropogenic activities. The conservation efforts for bryophytes are hampered by their slow growth rates. This study aims to investigate the potential of actinobacteria to promote the growth of bryophytes. In this study, three plant growth-promoting actinobacteria, Dermacoccus abyssi MT1.1^T, Micromonospora chalcea CMU55-4 and Streptomyces thermocarboxydus S3 were cultured in International Streptomyces Project medium 2 (ISP2) broth to obtain culture filtrates containing bioactive compounds for enhancing the growth of two bryophyte species, Physcomotrium sphaericum (C. Ludw.) Fürnr and Sphagnum cuspidatulum C. Müll. Interestingly, the incorporation of actinobacterial culture filtrates into 1/16 Murashige and Skoog (MS) medium yielded superior growth performance of P. sphaericum (C. Ludw.) Fürnr and S. cuspidatulum C. Müll, as observed from the thallus height, fresh weight, total chlorophyll contents, and total carotenoid contents compared to control groups. In addition, the inoculation of M. chalcea CMU55-4 on S. cuspidatulum C. Müll grown in sterile peat moss demonstrated the highest values for thallus height, fresh weight, dry weight, total chlorophyll content, and total carotenoid content. All actinobacteria successfully colonized the moss seedlings without any observable negative impacts, indicating beneficial interactions between actinobacteria and bryophytes. This research sheds light on the potential of harnessing plant beneficial actinobacteria to enhance the growth of bryophytes for conservation purposes.

Keywords: Bryophyte; Colonization; Deep-sea actinobacteria; Endophytic actinobacteria; Plant growth-promoting actinomycetes; Plant-microbe interactions.

Graphical abstract

Fig. 1

Growth of Sphagnum cuspidatulum C. Müll inoculated with (a) Sterile distilled water (control) (b) S. thermocarboxydus isolate S3 (c) D. abyssi MT1.1^T (d) M. chalcea CMU55-4.

Fig. 2

Neighbor-joining phylogenetic tree based on an almost complete 16S rRNA gene sequence of re-isolated actinobacteria and their related taxa. Bootstrap values are based on 1000 re-samplings.