Rare amino acid influences E. coli infection

January 12, 2015, University of Glasgow
Escherichia coli. Credit: Rocky Mountain Laboratories, NIAID, NIH

Scientists have discovered how a rare amino-acid in humans influences the behavior of the E.coli bacterium.

Most of the thousands of strains of E. coli are harmless, with many being a normal part of the in , however some strains can cause illness in humans.

Among the most well-known is E. coli O157, typically acquired via contaminated food, which causes severe diarrhea and can lead to .

The O157 strain only infects the gut so scientists at the University of Glasgow wanted to know what stopped it from spreading to other parts of the body.

The team led by Dr Andrew Roe, and PhD student James Connolly of the Institute of Infection, Immunity & Inflammation, analyzed the genome sequence of 1,500 strains of E.coli.

They wanted to see how the genes of the bug, which enable it to attach to and infect a host, responded to varying concentrations of D-Serine, an amino-acid produced in the brain where it plays a role in nerve signaling.

They found that E. coli O157 is unable to attach itself to host tissue in high concentrations of D-Serine. Other strains, such as those that cause meningitis, thrive in the presence of the amino-acid.

The discovery, published in the ISME Journal, opens up the possibility of altering the diet to increase levels of D-Serine to prevent E. coli O157 infection or perhaps treat it.

Dr Andrew Roe, senior lecturer, said: "This work provides new insights into the infection process with the aim of developing compounds that block such bugs from attaching to the host.

"With many strains of E. coli developing resistance to traditional antibiotics, such approaches are urgently needed.

"If we can disarm such bacteria rather than killing them it puts less pressure on the bacteria to evolve into something that is resistant to treatment."

E. coli O157 doesn't normally live in humans, instead residing in the gut of cattle. Eating contaminated food is the most common cause of infection but it can also be picked up in the environment, through contact with the bacteria in fields, for example.

The genetic variety between strains of E. coli is huge, with around 2,000 'core' genes and 18,000 genes that vary between strains. Different are able to attach themselves to different tissues, causing a range of different infections.

The bacterium can cause a wide range of infections including those of the gut, bladder, bloodstream and brain. These can be very common, for example, over half of all women suffer from E. coli associated bladder infections at some point in their lives.

Explore further: Microbiologists discover how gut bacterial resources are hijacked to promote intestinal illnesses

More information: Link to research paper in The ISME Journal: www.nature.com/ismej/journal/v … l/ismej2014242a.html

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1 / 5 (1) Jan 12, 2015
Nutrient-dependent/pheromone-controlled adaptive evolution: a model. http://www.ncbi.n...24693353

The model of chemical ecology extends the concept of nutrient-dependent RNA-directed DNA methylation to RNA-mediated cell type differentiation controlled by the metabolism of nutrients to species-specific pheromones. Pheromones control the physiology of reproduction via conserved molecular mechanisms in species from microbes to man.

Amino acid substitutions stabilize biophysically constrained protein folding that is perturbed by mutations, which others seem to think somehow lead to the evolution of biodiversity.
5 / 5 (1) Jan 12, 2015
Jamie K just can't stop himself from posting the same self-referencing spam.
1 / 5 (1) Jan 12, 2015
The amino acid substitution in E. coli requires three steps that link it to RNA-mediated stability of the DNA in the organized genome of a nutrient-dependent strain. As anyone who is not a science idiot knows or can learn, this is the process:

1) nutrient-dependent potentiation makes a trait possible,
2) receptor-mediated actualization makes the trait manifest via metabolism,
3) pheromone-controlled refinement/fixation makes it effective.

In the words of Blount, Barrick, Davidson, & Lenski, that process "...is probably typical..." of how many new functions arise. http://dx.doi.org...ure11514

Science idiots replace that 3-step process and claim that Lenski's experiments proved beneficial mutations cause evolution.

See for comparison Combating Evolution to Fight Disease http://www.scienc...88.short Dobzhansky (1973) noted that a single amino acid substitution differentiated the cell types of humans, gorillas, and chimpanzees.
1 / 5 (1) Jan 12, 2015
This research report links microbes (E. coli) to man (humans) via the conserved molecular mechanisms we first detailed in our 1996 Hormones and Behavior review "From Fertilization to Adult Sexual Behavior" http://www.hawaii...ion.html

Everything learned about physics, chemistry, and the conserved molecular mechanisms of cell type differentiation attests to the fact that nothing about RNA-directed DNA-methylation and RNA-mediated amino acid substitutions that differentiate cell types has changed during the past 18 years. That suggests it has never changed, and that the conserved molecular mechanisms link ecological variation to ecological adaptations without this pseudoscientific nonsense: "...genomic conservation and constraint-breaking mutation is the ultimate source of all biological innovations and the enormous amount of biodiversity in this world." (p. 199) http://www.amazon...99661731

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