Cluster formation in liverwort-associated methylobacteria and its implications

Area of Science:

• Microbiology
• Plant Science
• Symbiosis

Background:

• Pink-pigmented methylotropic bacteria, genus Methylobacterium, are known plant epiphytes.
• Their interaction with bryophytes, like liverworts, and its mechanisms are poorly understood.
• Methylobacteria are known to enhance plant cell growth.

Purpose of the Study:

• To isolate and identify Methylobacterium species associated with Marchantia polymorpha.
• To investigate the growth-promoting effects of these bacteria on liverworts.
• To explore unique characteristics of liverwort-associated Methylobacterium.

Main Methods:

• Isolation of Methylobacterium from Marchantia polymorpha thalli.
• Identification using 16S ribosomal RNA (rRNA) gene sequencing and polymerase chain reaction (PCR).
• Assessing growth-promoting activity on isolated liverwort gemmae and observing bacterial behavior in liquid culture.

Main Results:

• An undescribed species of Methylobacterium was isolated from Marchantia polymorpha.
• Both wild-type and type strain Methylobacterium significantly stimulated liverwort gemmae expansion by approximately 350%.
• Liverwort-associated Methylobacterium formed dense cell clusters in water, unlike Methylobacterium mesophilicum.

Conclusions:

• Liverwort-associated Methylobacterium are likely co-evolved symbionts.
• Bacterial cluster formation may be an adaptation for survival during drought periods in desiccation-tolerant plants.
• This interaction highlights a novel plant-microbe symbiosis in bryophytes.