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(Real non-Darwinian) evolution in action: Bacteria murder rivals and steal their genes

T6SS (green, magenta) mediated killing and lysis of competing bacteria can lead to DNA release (cyan) and subsequent gene transfer/U Basel, Biozentrum

From ScienceDaily:

Bacteria not only develop resistance to antibiotics, they also can pick it up from their rivals. In a recent publication in Cell Reports, Researchers from the Biozentrum of the University of Basel have demonstrated that some bacteria inject a toxic cocktail into their competitors causing cell lysis and death. Then, by integrating the released genetic material, which may also carry drug resistance genes, the predator cell can acquire antibiotic resistance.

The predator bacteria take up the released DNA fragments. If these fragments carry certain drug resistance genes, the specific resistance can be conferred upon the new owner. As a result, the antibiotic is no longer effective and the bacterium can reproduce largely undisturbed.

Pathogens with such abilities are a major problem in hospitals, as through contact with other resistant bacteria they may accumulate resistance to many antibiotics — the bacteria become multidrug-resistant. In the worst case, antibiotic treatments are no longer effective, thus nosocomial infections with multidrug-resistant pathogens become a deadly threat to patients. Paper. (public access) – Peter David Ringel, Di Hu, Marek Basler. The Role of Type VI Secretion System Effectors in Target Cell Lysis and Subsequent Horizontal Gene Transfer. Cell Reports, 2017; 21 (13): 3927 DOI: 10.1016/j.celrep.2017.12.020 More.

Antibiotic resistance has been marketed to the public as explicitly Darwinian, along with occasional cries of alarm raised about the future of public health science if anybody doubts Darwin.

One problem is confusing explanations. For example, from the terminology page at ScienceDaily, we learn,

Antibiotic resistance evolves naturally via natural selection through random mutation, but it could also be engineered by applying an evolutionary stress on a population.

Do we know that the mutations we observe are random or do we just assume that they are?

The resistance may indeed have arisen randomly billions of years ago. But it may now be part of a billennial library shared among bacteria with no recent common ancestor, by methods such as the one described above and many others.

Humans have only been developing antibiotics for less than a century.

Granted, we strategize and bacteria don’t. But the orders of magnitude between a century and a billion years may give randomness the favorable odds it doesn’t usually have: However, only a few bacteria need solve the problem provided that the solution remains in the system via horizontal gene transfer. But horizontal gene transfer is not Darwinism (natural selection acting on random mutation), assumed to be passed on to lineal descendants.

A ready resort to Darwinism may hinder us from finding out the specifics. The ScienceDaily page continues:

Once such a gene is generated, bacteria can then transfer the genetic information in a horizontal fashion (between individuals) by plasmid exchange.

Indeed. The Darwinism (natural selection acting on random mutation) path may be quite narrow and the horizontal gene transfer path may be quite broad. From an information perspective, if such a model is correct, it would make lot of sense: Most bacteria do not need to acquire the information by improbable series of events occurring within themselves individually.

We look forward to a thoughtful discussion.

See also: Researchers ask: Do viruses share genes across the kingdoms of life?


Horizontal gene transfer: Sorry, Darwin, it’s not your evolution any more

This does not bode well for humans. Mung

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