Bacterial cells have colonized every part of our world. But even though some can evade disinfectants to live in NASA cleanrooms, others are very challenging to grow in the lab environment. Scientists are now gaining many new insights into the survival requirements and strategies of bacteria.
Why are Some Microbes so Difficult to Grow in the Lab? It May Take a Village.
Researchers often cultivate microbes for specific purposes in the laboratory. Some can be used to generate large amounts of genetic tools known as plasmids, for example. These laboratory workhorses are often engineered for such purposes.
But in may other cases, scientists want to learn more about the function of different microbes, such as those that grow in the human gut, or novel microbes like archaea the are discovered in unique environments. Researchers usually need to cultivate large numbers of these microorganisms to study them effectively, and this can be very difficult.
A new report published in the Proceedings of the National Academy of Sciences (PNAS) has shown that some of these microbes that are so challenging to grow actually need a community to survive. Some bacteria rely on a network of relationships, and these connections provide support that is not always evident. When a single microbe is lost from some of these communities, the entire group collapses. A microbiome can either thrive or die together, the work suggested.
Environmental and Genetic Factors Trigger Changes That Offset
Researchers exposed 115 genetically unique strains of Escherichia coli bacteria to 135 nutrient combinations, with varying amounts of 48 different chemicals. Machine learning was used to analyze 14,000 growth profiles, and determine how the various combinations of chemical nutrients affected bacterial growth.
This work, which was reported in Communications Biology, showed that the influence of these different chemicals laregly depended on how much glucose (sugar) was available; it has a major impact on bacterial growth. But while some growth changes are observed because of various genetic or chemical factors, the changes induced by these factors tended to offset or counterbalance each other.
Slow-growing Bacteria Are More Reactive to Their Environment
Microbes can adapt to environmental conditions with changes in gene regulation; they can detect signals in environment, and alter genes expression in response. The findings have been reported in Science Advances.
This work showed that a cell's growth rate affects signaling molecules in the cell. When a cell grows quickly, molecules get diluted in the cell, which dampens the signals from the environment, and reduces how the cell reacts to the environment. But when cells grow slowly, the molecules are less diluted and they persist, which heightens the cell's sensitivity to the environment.
In NASA Cleanrooms, Tough Microbes Find a Way to Live
Scientists have analyzed microbes that were recovered from NASA cleanrooms. Unsurprisingly, they carried genetic characteristics that allowed them to survive radiation and various stringent cleaning chemicals. Some of these microbial genes promoted DNA repair, others were related to detoxification, and some improved metabolic functions, which all boosted survival under harsh conditions.
The microbes in this study might be helpful to us in biotechnology or industry, and could help scientists learn more about the types of microbial cells that might be present on space missions. The work was reported in Microbiome.
Sources: PNAS, Communications Biology, Science Advances, Microbiome
