Tag: bacteria (page 5 of 5)

resistant bacteria from labs enter rivers in china

bacteria

In China, resistant bacteria from molecular biology experiments are turning up in rivers and streams. Molecular biologists use different resistant strains in order to clone bacteria and produce different proteins. In the US, academic and industrial labs have implemented steps to prevent these resistant genes from being introduced into our environment. China, it appears, still has a ways to go before they get a handle on this. From C&EN:

But because this technique is still commonly used in molecular biology labs, some researchers have been concerned that these experiments could release resistance genes into the environment. To search for antibiotic-resistance genes introduced by synthetic plasmids, Jun-Wen Li at the Institute of Health and Environmental Medicine, in Tianjin, China, and his colleagues took water samples from six Chinese rivers downstream of densely populated cities. They extracted plasmids from the samples and transferred the DNA into Escherichia coli. Then they screened the bacteria for a gene commonly used in academic and industrial labs that confers resistance to the antibiotic ampicillin. To determine if a gene in a sample came from a manmade source, they used polymerase chain reaction to look for sequences unique to several synthetic plasmids.

The researchers found synthetic resistance genes in all six rivers. Of all of the ampicillin-resistance plasmids they found in the rivers, about 27% had the synthetic vector-sourced gene.

More here.

arsenate or phosphate controversy put to bed

Arsenate

A while back some scientists thought they had discovered a bacteria that could thrive on arsenic. They hypothesized that arsenic was being incorporated into the organism’s molecules in place of phosphorus without any problem. This was later discovered to be incorrect. A paper in Nature Magazine details how bacteria discriminate between arsenic and phosphorus.  From Scientific American:

“This work provides in a sense an answer to how GFAJ-1 (and related bacteria) can thrive in very high arsenic concentrations,” say Tobias Erb and Julia Vorholt of the Swiss Federal Institute of Technology in Zurich, co-authors of the latest paper, who were also co-authors on a follow-up paper that cast doubt on the initial arsenic-life claims.

The researchers looked at five types of phosphate-binding protein — which bind phosphate in a molecular pathway that brings it into the cells — from four species of bacteria. Two of the bacterial species were sensitive to arsenate and two were resistant to it. To test how effective these proteins were at discriminating between phosphate and arsenate, the researchers put them in solution with a set amount of phosphate and different concentrations of arsenate for 24 hours, and then checked which of the molecules the proteins would bind to.

Their threshold for when ‘discrimination’ broke down was when 50% of the proteins ended up bound to arsenate — indicating that the ability to discriminate had been overwhelmed. Even in solutions containing 500-fold more arsenate than phosphate, all five proteins were still able to preferentially bind phosphate. And one protein, from the Mono Lake bacterium, could do so at arsenate excesses of up to 4,500-fold over phosphate.

The paper includes detailed structures of both phosphate and arsenate bound to bacterial protein. You can see how the arsenate’s larger size impedes protein binding. Please check out the source link for more.

resistant bacteria are as old as time

Inside the Lechuguilla cave

Antibiotic resistant bacteria are an increasing threat to our health care system. Because antibiotics are over-prescribed and also administered to livestock in their feed, bacteria have developed mechanisms to withstand antimicrobial drugs. As bacteria evolve to evade current antibiotics they become harder and harder to treat. While this may appear to be a problem created by modern medicine, there is evidence that the ability to develop drug resistance mechanisms is hard wired in bacteria. A group of scientist have uncovered species of drug resistant bacteria in a 4 million year old cave. From Scientific American:

But the capacity to fend off antibiotics might actually be lodged deep in bacteria’s evolutionary history. A new study has uncovered dozens of species of bacteria in a 4 million-year-old cave that harbor resistance to both natural and synthetic antibiotics.

A team of researchers descended to 400 meters in distant, untrafficked reaches of Lechuguilla Cave in New Mexico to collect samples of bacteria. Few people have entered the cave’s deepest regions since its discovery in 1986, and surface water takes thousands of years to percolate through the nearby dense Yates Formation rock down to the cave. As a consequence, the area is a prime place to study naturally occurring antibiotic resistance, noted the researchers, whose results were published online April 11 in PLoS ONE.

Wright and his colleagues found that of the 93 bacterial strains tested from the cave, most were resistant to more than one of the 26 different antimicrobials. And some bacteria were resistant to more than a dozen antibiotics used by doctors, such as telithromycin, ampicillin and daptomycin, which is currently a treatment of last resort to combat resistant infections. The cave bacteria were not likely to cause infection in humans, but could provide the genetic traits that confer resistance to that are.

Check out the research article on PLoS ONE.

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