Gut bacteria adapting to New Zealanders' love of fruit and veg

19 February 2019

The discovery of the first gut bacterium that specialises in breaking down a hard-to-digest substance found in plants suggests that the human gut microbiome is evolving to accommodate our consumption of fibre-rich foods. 

Plant & Food Research scientists, in collaboration with New Zealand and international research partners, discovered a new human gut bacterium Monoglobus pectinilyticus ‒ the first specialist bacterium for pectin degradation and utilisation.

Pectin is a plant’s natural barrier to protect against bacterial attacks. It is also a primary source of dietary fibre for humans. This structurally complex carbohydrate is not a palatable food source for most bacteria as it is not high in energy. Yet, gut bacteria face the dilemma of having to break down the pectin barrier in order to access and digest nutritious plant materials for survival. How gut bacteria get around this problem is important for human health and increasing nutritional yields from dietary plants.

M. pectinilyticus is a dedicated microorganism for breaking down pectin, a dietary fibre that makes up 40% of the plant cell wall in common fruits and vegetables such as kiwifruit and tomato,” says Dr Caroline Kim, the Plant & Food Research scientist who leads the project. “The process wasn’t well-understood until now because few pectin-degrading bacteria exist and none as specialised as M. pectinilyticus.

“This had left a large gap in our knowledge of how this abundant and important component of human diet is used inside our bodies. The high degree of specialisation shows that the typically abundant pectin consumption in the human diet may have placed evolutionary pressure on our gut microbiome to make room for specialist bacteria with dedicated niche and function for pectin degradation. Since M. pectinilyticus only utilises pectin and no other types of carbohydrates, this organism will provide valuable insights into how gut microbes interact with plant pectin and ultimately begin the process of plant digestion in the human colon.”

The team analysed the faecal samples and dietary intakes of 44 healthy people in New Zealand over 10 weeks. They found that the presence of M. pectinilyticus positively correlates to the participants’ pectin consumption - the more fibre one eats, the more likely that this beneficial microorganism is present. 

The study, “Genomic insights from Monoglobus pectinilyticus: a pectin-degrading specialist bacterium in the human colon”, is published in the February 2019 issue of The ISME Journal, a top academic journal in microbial ecology (https://doi.org/10.1038/s41396-019-0363-6).

Photo caption: M. pectinilyticus peels off the pectin layer (middle lamella) from the plant cell walls of orange peels.

Contact:
Nickkita Lau
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Plant & Food Research Mt Albert,
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Auckland, 1025, New Zealand
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