A new study from Vanderbilt University has revealed that bacteria can develop a heightened sensitivity to acid levels when exposed to extreme environmental conditions. This sensitivity triggers a cascade of gene expression, allowing the microbes to adapt to constantly changing environments.
Researchers led by microbiologist Sarah Worthan pushed Escherichia coli (E. coli) bacteria to the brink by subjecting them to cycles of long-term starvation followed by exposure to nutrient-rich environments. Over time, some bacterial populations evolved genetic mutations that enhanced their ability to thrive under these challenging conditions.
“These mutations appear to rapidly coordinate complex physiological responses through pH sensing, shedding light on how cells use environmental cues to adapt,” the researchers wrote.
The study exposed 16 populations of E. coli to extreme conditions over 300 days. As the bacteria starved, their environment’s pH levels shifted dramatically. One particular mutation a change in a protein-building block from arginine to histidine in the Rho protein arose in seven bacterial populations. This mutation affected the bacteria’s ability to manage protein production under feast-and-famine conditions.
The mutated ydcI gene, which also emerged in response to pH changes, played a crucial role in allowing the bacteria to adapt to fluctuating environments. The ydcI gene helps cells better tolerate changes in the Rho protein and may act as a switch triggered by environmental pH shifts.
This mechanism of adaptation has been observed in nature, such as in the bacteria Bartonella bacilliformis, which causes Carrion’s disease. The bacteria must rapidly adjust its internal pH when transitioning from the insect gut to human blood, showing how pH sensing can be vital for survival.
Worthan and her team noted similarities between bacterial adaptations and how cancer cells create favorable environments by adjusting their internal pH. This study demonstrates the potential for experimental evolution to uncover crucial mutations that help organisms, and even cancer cells, thrive in challenging environments.
The findings were published in Proceedings of the National Academy of Sciences (PNAS).
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