Plants found to carry bacteria in their cells

Indian and Australian scientists have described how healthy plants appear to carry bacteria in their cells, opening a new avenue of research to improve future plant health and propagation efforts — including food crops such as grains and fruit such as grapes.

The milestone study first commenced at Flinders University 10 years ago, when visiting scientist Dr Pious Thomas worked together with Professor Chris Franco. They used various high-tech laboratory methods to describe how endophytic bacteria can exist inside plant cells, leading to the concept of ‘alien life’ in healthy plant cells.

“It’s baffling how this bacterial association in cell cultures escaped the attention of plant biologists and microbiologists considering that this is a widespread phenomenon in plant tissue cultures we tested, and the in vitro cultures have long been used in both basic and applied research,” Prof Franco said.

Writing in the journal Microorganisms, Prof Franco and Dr Thomas say cytobacteria (which they call Cytobacts) have been widely observed in micro-propagating stocks in crops including banana and papaya. With Dr Thomas now serving as CEO and Director of the Thomas Biotech & Cytobacts Centre for Biosciences in Bengaluru, he is keen to put these observations to good use.

“I am excited to expand this new field of plant cell biology in my R&D centre at Bengaluru, with the plan to focus on endophytic microorganisms and allied areas with a primary focus on micropropagation of papaya, which is severely hampered due to interference from microbial contaminants,” Dr Thomas said.

“Normally the endophytic bacteria are known to reside between plant cells. Because plant cells are considered to be free of other living organisms, it goes against the grain to report bacteria within plant cells.

“We need new tools to be able to study the role of these intracellular bacteria in healthy plants, which are not normally amenable for conventional microbiological methods.”

“This new paradigm of cytobacteria in healthy cells has the potential to open up a whole new area of research, including plant biology, human health and environmental microbiology,” Prof Franco added. He said the study suggests that Cytobacts have possibly adapted in plant species after losing some of their functions and ability to synthesise compounds so they become obligate symbionts of the plant cell.

“Potentially they are involved in some of the integral functions of plants, such as energy metabolism, or as an inducer of defence responses against other microorganisms,” he said.

Image credit: ©stock.adobe.com/au/WR.LILI

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