Bacterial Intelligence? making decisions chemically (General)

by David Turell , Sunday, April 28, 2019, 20:46 (1819 days ago) @ David Turell

Chemical sensing and reactions guide bacteria:

https://www.sciencedaily.com/releases/2019/04/190423133557.htm

Although they are considered the simplest of all life forms, even microorganisms sense their environment and are able to actively move within it. This allows them to identify both food and harmful substances and to move towards or away from them, guided by the concentration gradient of the substance in their environment. The journey of many microbes can thus be viewed as a sequence of decisions based on chemical gradients. (my bold)

The ability of cells to target or avoid particular substances is called chemotaxis. Until now, scientists have generally considered the chemotactic properties of bacteria to be a common feature of a species or population -- as if all cells behaved more or less the same. In this case, average values are sufficient to describe their movement behaviour. Now, researchers at ETH Zurich have observed the chemotaxis of bacteria in a behavioural experiment. "If you look with the appropriate technology, you'll find astonishing behavioural differences even within a population of genetically identical cells,"

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they have developed a special microfluidic system that allows them to observe the movement of thousands of individual bacteria in a liquid at extremely small scales. The system comprises a series of narrow channels that branch out on to a thin glass plate to form a sort of microscopic maze through which the bacteria swim.

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The bacteria all start in the same place -- and visibly divide up within the channel system as they are forced to decide at each fork whether to swim up or down the gradient of attractant. The bacteria owe their chemotactic abilities to specialised receptors that allow them to identify the attractant. In addition, they have about half a dozen flagella, which can rotate eithe ETH researchers found individuals that were able to follow the attractant well (by navigating towards the higher concentration whenever they came to a fork), and those that were less able to negotiate the maze. The scientists attribute these behavioural differences to variations in the genetic activity of identical genes in sister cells. This means the cells have different amounts of the corresponding proteins. "There is biochemical noise in every cell. As a fundamental random component, this causes diversity of appearance and behaviour," say the researchers.her clockwise or anti-clockwise. "Based on this, the bacterium changes its direction or continues to swim in one direction," explain Salek and Carrara.

Even within a group of genetically identical cells -- that is, clones -- the ETH researchers found individuals that were able to follow the attractant well (by navigating towards the higher concentration whenever they came to a fork), and those that were less able to negotiate the maze. The scientists attribute these behavioural differences to variations in the genetic activity of identical genes in sister cells. This means the cells have different amounts of the corresponding proteins. "There is biochemical noise in every cell. As a fundamental random component, this causes diversity of appearance and behaviour," say the researchers.

Diversity, or heterogeneity, of chemotaxis may provide an evolutionary advantage for the bacteria, since although those skilled at chemotaxis can quickly locate and exploit locally stable food sources, their sister cells less affected by the attractant are more likely to venture into new territory, where they may encounter additional food sources in a constantly changing environment.

"Non-genetic diversity has long been known in the biomedical life sciences; for example, it is thought to play a role in antibiotic resistance. Now, environmental scientists have shown that this diversity also affects fundamental behaviours of bacteria, such as locomotion and chemotaxis -- further expanding the concept of bacterial individuality," says Stocker.

Comment: Note that this study shows chemical decisions caused by underlying variations in bacteria of their genetic makeup. It adds to my evidence as to why antibiotic resistance develops. The 'intelligence' of their decisions is all in their individual makeup.