Saturday, October 23, 2010

UCLA-LED RESEARCH TEAM FINDS THAT BACTERIA CAN STAND UP AND WALK

0 comentarios

Many drug-resistant infections are the result of bacterial biofilms, structured aggregates of bacteria that live on surfaces and that are extremely resistant to environmental stresses. These biofilms impact human health in many ways — cystic fibrosis, for example, is a disease in which patients die from airway bacterial biofilm infections that are invulnerable to even the most potent antibiotics.

Now, UCLA researchers and their colleagues have found that during the initial stages of biofilm formation, bacteria can actually stand upright and "walk" as part of their adaptation to a surface.

"Bacteria exist in two physiological states: the free-swimming, single-celled planktonic state and the surface-mounted biofilm state, a dense, structured, community of cells governed by their own sociology," said Gerard Wong, a professor of bioengineering at the UCLA Henry Samueli School of Engineering and Applied Science and at the California NanoSystems Institute at UCLA.

"Bacteria in biofilms are phenotypically different from free-swimming bacteria even though they are genomically identical. As part of their adaptation to a surface and to the existence of a community, different genes are turned up and down for bacteria in biofilms, leading to drastically different behavior," he said.

In the study, which appears in the current issue of the journal Science, Wong and his research group describe the new surface adaptation — the "walking" motility mechanism, which was observed in Pseudomonas aeruginosa, a biofilm-forming pathogen partly responsible for the lethal infections in cystic fibrosis.

What enables this upright walking are appendages called type IV pili, which function as the analog of legs. What's more, walking allows P. aeruginosa to move with trajectories optimized for surface exploration, so that they can forage more effectively. The upright orientation is also the first step in surface detachment for bacteria.

"We've shown that vertical orientation plays a critical role in key life-cycle events: vertically oriented bacteria can more readily detach from surfaces, allowing them to spread and disperse effectively," said Jacinta Conrad, a former postdoctoral researcher with Wong's group and an assistant professor of chemical and biomolecular engineering at the University of Houston. "Our unique contribution is to directly relate single-cell behavior to specific events in the bacterial life cycle and thereby show how single-cell motility influences biofilm morphology."

The research team was able to develop a series of search engines and computer programs that use particle-tracking algorithms to quantitatively analyze time-lapse microscopy movies of bacterial motion on surfaces.

"Previously, graduate students had to look at cells manually and then laboriously track them from one frame to the next," Wong said. "Our computational approach allows us to increase the volume of data analyzed 100,000-fold and to perform the necessary analysis in a few hours rather than a few months.

"Moreover, we make sense of this mountain of information using search engine–based approaches. This represents a big advance in the way microscopes are used."

The work was conducted in collaboration with a research group at the University of Notre Dame led by Joshua Shrout, an assistant professor in the department of civil engineering and geological sciences and at the Eck Institute for Global Health.

"P. aeruginosa infections are unfortunately the leading cause of death for individuals with cystic fibrosis," Shrout said. "In addition to these lung infections, P. aeruginosa also causes skin, eye and gastrointestinal infections. As we learn how P. aeruginosa colonizes surfaces, perhaps we can develop better methods to treat these infections."

"One of the most exciting factors of this work for me is the potential for widespread impact," Conrad said. "Biofilm formation is ubiquitous in human health and also in a variety of industrial settings. Biofouling due to biofilm formation increases the hydrodynamic drag on ships, leading to increased fuel consumption, and also contributes to increased costs in water treatment, oil recovery and food processing. Controlling biofilm formation will therefore allow us to reduce biofouling-related problems across a wide range of industries."

(Photo: UCLA)

UCLA

MEN PERSPIRE, WOMEN GLOW

0 comentarios
Women have to work harder than men in order to start sweating, while men are more effective sweaters during exercise, according to new research published in the journal Experimental Physiology.

The study by Japanese scientists at Osaka International University and Kobe University looked at differences between men and women's sweating response to changes in exercise intensity. The researchers asked four groups of subjects (trained and untrained females, trained and untrained males) to cycle continuously for an hour in a controlled climate with increasing intensity intervals.

The results showed that men are more efficient at sweating. While exercise training improves sweating in both sexes, the degree of improvement is greater in men, with the difference becoming even more pronounced as the level of exercise intensity increases. The untrained females had the worst sweating response of all requiring a higher body temperature than the other groups (or work intensity) to begin sweating. In other words, women need to get hotter than men before they get sweaty.

The study's coordinator Yoshimitsu Inoue commented: 'It appears that women are at a disadvantage when they need to sweat a lot during exercise, especially in hot conditions.'

Previous studies have demonstrated that men have a higher sweat output than women, in part because testosterone is believed to enhance the sweating response. Physical training is known to decrease the body's core temperature threshold for the activation of the sweating response, which works to the athlete's advantage and allows them to perform longer. This is the first study, however, to investigate the sex differences in the effects of physical training on the sweating response during exercise.

The findings have implications for exercise and heat tolerance in humans, including shedding light on why the sexes cope differently with extremes of temperature like heat waves.

Inoue believes there may be an evolutionary reason why men and women have evolved to sweat differently. 'Women generally have less body fluid than men and may become dehydrated more easily,' he explains. 'Therefore the lower sweat loss in women may be an adaptation strategy that attaches importance to survival in a hot environment, while the higher sweat rate in men may be a strategy for greater efficiency of action or labour.'

Inoue says future studies will look more closely at the relationship between reproductive hormones and the sweating response as well as the effectiveness of different kinds of sweat (sweat that evaporates and cools versus sweat that drops off).

In the meantime, Inoue advises women should take more care than men in hot conditions. But he adds, 'Both men and women can acclimate themselves better to heat if they exercise regularly before a heat wave comes.'

Wiley-Blackwell

SO THAT'S WHY WE'RE ALLERGIC TO SUN CREAMS

0 comentarios
What happens to sunscreens when they are exposed to sunlight? And how is the skin affected by the degradation products that form? This has been the subject of research at the University of Gothenburg and Chalmers University of Technology that will be presented at the upcoming dermatologist conference in Gothenburg.

A growing hole in the ozone layer and a change in sunbathing habits have brought an increase in the number of cases of skin cancer worldwide. One way of dealing with this has been to advocate sunscreens, though greater use of these products has triggered an increase in contact allergy and photocontact allergy to sun protection products.

"We know that sun creams pass through the skin into our bodies, but we don't know what effects they have on us," says Isabella Karlsson, doctoral student at the Department of Chemistry at the University of Gothenburg's Faculty of Science. "Many of them actually break down in the presence of sunlight. We therefore wanted to look at what can happen to the chemical sun protection agents when exposed to UV rays, and how the degradation products that form affect the skin."

In their study, the researchers have come up with an explanation of what happens during this process.
"Arylglyoxales, one of the degradation products, turned out to be highly allergenic," says Karlsson. "Which could explain why some people are allergic to creams that contain dibenzoylmethanes, one of the UVA-absorbing substances in sun creams."


This has made for a better understanding of the mechanism behind photocontact allergy, which could lead to a product that does not cause allergy, and could determine which sun creams people are most likely to be sensitive to.

But their discovery is already having an impact. The healthcare system has long found it difficult to test patients with suspected photocontact allergy, but thanks to the study a new test is being developed.
"We're just starting to work with various dermatology clinics on assessing the test," explains Karlsson. "So more patients will be able to find out whether they have photocontact allergy, which could help them in their everyday lives and reduce the burden on the healthcare system."

University of Gothenburg

Followers

Archive

 

Selected Science News. Copyright 2008 All Rights Reserved Revolution Two Church theme by Brian Gardner Converted into Blogger Template by Bloganol dot com