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NatureScience

Bacterial Colony Aging And Diversity Explored By New Research

If you’ve ever pondered the seemingly great similarities between large-scale human settlements — such as cities — and bacterial colonies, then new research from INSERM may interest you.

The new work is the first to track the life of individual bacterial cells in a colony as that colony ages, diversifies, and slowly collapses for lack of new resources. Certainly easy to draw comparisons between such phenomena and the phenomena of human civilizations/cultures.

Tersicoccus phoenicis, new bacterium

The press release provides more:

Like human societies — think New York City — bacterial colonies have immense diversity among their inhabitants, often generated in the absence of specific selection pressures.

Microbiologists have long been aware of this phenomenon, and they credit it as a reason microbes have been able to colonize almost every conceivable terrestrial habitat from underground Antarctic lakes to hot springs to intensely radioactive pools, says corresponding author Ivan Matic, of INSERM, Paris. But none had tried to track it at the level of single cells.

“By using up to date experimental tools that allowed us to follow individual living cells, we were able to enter into this amazing, beautiful world of bacterial multicellular structures,” states Matic. “We observed massive phenotypic diversification in aging Escherichia coli colonies. Some variants showed improved capacity to produce biofilms, whereas others were able to use different nutrients, or to tolerate antibiotics, or oxidative stress, compared to the ancestral strain.”

For the new research, the scientists began each of the colonies being monitored with a “small number of identical cells, and observed them as they grew and as the colony aged. An aging colony is one where growth has stopped, because nutrients have been exhausted and/or toxins have accumulated.”

“At this point most cells in the colony stop dividing and dead cells accumulate,” notes Matic.

Even during some of the earlier phases of their development colonies are quite environmentally diverse. “For example, since it grows on a solid medium, nutrients diffuse from the bottom up, resulting in a nutritional gradient with lower levels at greater elevation above the medium. Similarly, oxygen and UV radiation decline with distance from the colony’s surface, so that cells close to the top have ample oxygen, while those well below exist under anaerobic conditions.”

And, something else interesting to note, in the aging colonies the increasing levels of toxins and falling levels of nutrients aren’t homogeneously distributed. (You can certainly draw a comparison with declining civilizations there. Reminds me of the famous saying: “The ‘future’ is already here, it’s just not evenly distributed.”)

“We showed that the rare survivors of a senescent colony are very diverse and are different from their ancestors,” states Matic. “We found different metabolic capacities, different levels of stress resistance, improved capacity to produce biofilms, and the ability to use different nutrients. Some of these capacities probably evolved due to obvious selection pressures, such as utilization of alternative energy sources.”

The new findings were just published in the Journal of Bacteriology.




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