MODIFIED bacteria could form a living barrier against would-be invaders such as HIV and TB, say researchers in Italy. They have shown that a bacterium altered to produce antibodies can cure thrush.

Vaginal thrush is caused by the yeast Candida albicans . Although it can be treated with antifungal drugs, the disease often flares up repeatedly in susceptible women. Candida also causes mouth infections and can be life-threatening in people with AIDS.

Luciano Polonelli at the University of Parma and his colleagues had made an antibody that mimics the action of a toxin that kills a wide range of bacteria and yeasts. To treat thrush in rats, though, the team had to give repeated doses of the antibody.

So the group engineered Streptococcus gordonii , a harmless bacterium that lives in the mouth, to secrete the antibody. In rats, the engineered bacteria were just as effective at curing vaginal thrush as standard drugs.

Polonelli thinks you could treat various diseases this way, such as gut infections. And although the modified S. gordonii disappeared after a month, engineered bacteria that permanently colonise the vulnerable mucous membranes that line the mouth, gut, lungs and vagina could provide long-term protection against diseases such as HIV

BIOLOGISTS in Australia have discovered that ants produce antibiotics to control diseases in their colonies. Trials in a Sydney hospital have already shown that these antibiotics are effective against a wide range of organisms, especially fungi, that cause diseases in humans. In particular, they kill the fungus Candida albicans, which is common in humans and, causes 'thrush', an infection of the mucous membranes.

Andrew Beattie of Macquarie University in Sydney studied more than a dozen species of ant. He was interested in discoveringwhy it is that ants play almost no part in pollinating flowers, while bees and wasps, their close relatives, do such an important job. Beattie found that pollen dies when it touches an ant's body. In every species he studied, it was secretions from metapleural glands, at the rear of the ant's thorax, that killed the pollen.

Beattie found that the secretion is an antibiotic, called metapleurin, which the ants use to prevent the fungi and bacteria from growing in their bodies. The substance is a lipid molecule, which is quite different from other antibiotics. Apart from protecting the ants, metapleurin has the side effect of making pollen less viable and able to germinate, so it dies.

One exceptional species of ant, which lacks metapleural glands, turns out to be an important pollinator. Beattie's collaborator, Rod Peakall of the University of Western Australia, has found that the winged male ant of this species, Myrmecia urens, pollinates a common orchid of southern Australia. M. urens pollinates up to half of the orchid's flowers.

When Beattie realised that the secretions of the metapleural glands had antibiotic properties, he took them to chemists to be analysed. He also asked medical colleagues at Westmead Hospital in Sydney to test how effective they were against bacteria that cause disease.

The hospital's initial screening tests against more than 300 of these bacteria have produced both good and bad results. Unfortunately, most of the bacteria are unaffected by the antibiotics. The good news is that metapleurin is highly effective against several strains of a common bacterium, Staphylococcus aureus, that are resistant to other antibiotics. These bacteria can be a major problem, sometimes preventing wounds from healing for many months after surgery.

Since the initial trials of the antibiotic, Beattie has talked with a major pharmaceuticals company in Britain. The company's main interest lies in the antifungal properties of metapleurin, because there are currently very few effective drugs to treat internal fungal infections, which can be fatal. The company challenged Beattie to show that ant antibiotics stop human fungal infections. The results of tests at Westmead Hospital are just emerging.

Two weeks ago, Beattie heard the news that a component of metapleurin had proved highly effective against C. albicans. Metapleurin also worked for the treatment of infections of the skin and internal tissues. Tests against other fungal organisms are under way.

SELF-defence chemicals produced by a sponge could be used as anti-fungal drugs, say researchers in Florida. They hope the chemicals could be used against the growing army of drug-resistant infections.

Peter McCarthy of Harbor Branch Oceanographic Institution in Florida and his team scoured the seas for new anti-fungal drugs. They collected samples of sponges and other invertebrates from waters down to depths of 1 kilometre. "Once you get to deep water, you're dealing with a lot of organisms that have never been seen by science," says McCarthy.

After identifying the samples, McCarthy and his team prepared chemical extracts which they sent to Denver-based company MycoLogics for analysis. The extracts were tested on two notorious human pathogens: Candida albicans , which causes skin infections and thrush, and Aspergillus fumigatus , which causes dangerous lung infections in people with weakened immune systems.

After screening more than 3500 extracts, MycoLogics identified 101 interesting candidates. The most promising of these were a completely new class of anti-fungal agents called cyclic peroxy acids, which killed off both species in the test tube and act differently from many anti-fungals. The animal that makes the compounds is Plakinistrella , an unassuming black sponge that lives in the seas off the Seychelles.

The team has yet to measure the efficacy and toxicity of the compounds in people. However, McCarthy says that spotting a new Achilles' heel in fungi is a rare and valuable insight.

Nestlé of Switzerland says its researchers were surprised to discover a simple and safe treatment for skin infections caused by Staphylococcus or Streptococcus bacteria and Candida yeasts (WO 02/05839). Instead of using antibiotics or disinfectants to kill the organisms, Nestlé has developed a cream containing a derivative of casein, the main protein in milk, which stops the organisms sticking to the skin surface. A few per cent by weight of the calcium or sodium salts of the casein derivative work particularly well, and can be used either to cure existing infections or in cosmetics to prevent them starting.

Probiotic bacteria given to babies with eczema at weaning can alleviate their symptoms, according to Finnish research.

The team at the University of Turku, Finland, analysed the gut flora of 13 babies with eczema. Stool samples were taken from all the babies before weaning and analysed for levels of "unfriendly" gut organisms, particularly Escherichia coli and other human gut pathogens.

Previous work has shown that high levels of these bacteria can stimulate the immune system to boost production of IgE antibodies, which are involved in causing allergic reactions.

The babies were weaned onto hydrolysed whey formula feed. Seven were also given supplements of Bifidobacterium lactis - a common benign bacterium found in the gut of healthy people. After four months, the infants' gut bacteria and IgE concentrations were analysed.

The babies receiving the probiotic supplements had significantly reduced levels of E. coli and bacteriodes in their stool samples - and significantly lower levels of IgE antibodies.

Simon Murch, a paediatric gastroenterologist at the Royal Free Hospital in London says the results are "interesting", but not unexpected. But, he says, the findings conflict with other research on allergy and gut bacteria.

One unpublished 20-year follow-up study in Prague has shown that E. coli given to babies at birth reduces allergy later in life. "Two E. coli formulae are commercially available in Czechoslovakia and are frequently given to infants there," Murch told New Scientist.

Journal reference: Gut (vol 51, p 51)

A HUMBLE yeast that has dared to rewrite the "universal" genetic language of DNA is more resistant to stress as a result, researchers say. Their work reveals a fast-track mechanism that organisms can use to evolve, raising new fears about the speed with which harmful microbes can develop resistance to drugs.

Biochemists are taught that all living things employ a common language or code when they read information in DNA and use it as a blueprint for assembling proteins. Francis Crick, the co-discoverer of DNA's structure, suggested in 1968 that organisms would die if they developed deviations in this language, as proteins would be mis-assembled and the organism would be too freakish and "unfit" to survive.

But in 1993, Manuel Santos and Mick Tuite at the University of Kent showed that the code is not universal. The team discovered deviations from the norm in a strain of Candida albicans , the yeast that causes thrush and other fungal infections. They found that proteins from the yeast often contain the amino acid serine where leucine would have been expected. Now Santos and his colleagues have shown that this makes the yeast "fitter" than its more conventional relatives.

Cells assemble proteins by reading the recipes encoded in messenger RNA (mRNA), a single-stranded copy of the original DNA. The cell works out which amino acid to add next by reading "codons"—triplets of adenine (A), guanine (G), cytosine (C) and uracil (U), the four bases of mRNA.

The yeast strain isolated by the Kent team broke the rules by misreading the codon CUG, which usually corresponds to the amino acid leucine. The yeast often added serine to the chain instead.

Santos and his colleagues have pinned the blame on a mutant form of transfer RNA (tRNA), a molecular shuttle that delivers amino acids to the growing protein chain. They transplanted the mutant gene for the tRNA from C. albicans into baker's yeast ( Saccharomyces cerevisiae ), which is easier to grow in the lab. The mutant tRNA's molecular architecture meant that it could load serine as well as leucine into the growing protein.

As a result, the altered S. cerevisiae could potentially load 50 000 serines into proteins instead of leucine, which should have spelt catastrophe for the baker's yeast. Instead, it tolerated stresses such as high temperatures, heavy metals, powerful oxidising agents and a laboratory antibiotic called cyclohexamide. Natural baker's yeast died when exposed to the same stresses. "People said such changes would be lethal, but we've shown it's advantageous," says Santos, who is now at the University of Aveiro in Portugal.

"We think that the serine-rich proteins are detected by molecular sensors in the yeast which trigger a general stress response," says Santos. This would explain how the yeast becomes so resistant to the stresses. The team's work will appear in Molecular Microbiology .

Variants of the genetic code could be widespread. "We believe there are many more genetic code changes, as they provide accelerated development of new phenotypes," says Santos. He adds that microorganisms might use it as a fast-track ploy for developing traits such as antibiotic resistance.

PEOPLE who bake bread and fail to wash their hands afterwards are at risk of picking up a nasty yeast infection.

Thrush, an infection of the mouths of infants or of the vagina, is usually caused by the fungus Candida albicans . But microbiologists in Italy and the US have now shown that commercial strains of baker's yeast, Saccharomyces cerevisiae , can also cause the disease. "Most people don't realise baker's yeast is a live organism because it comes in a powder or a cake mix," says Karl Clemons of the Santa Clara Valley Medical Center in San Jose, California.

Clemons and his team decided to investigate baker's yeast after seeing isolated reports of it causing thrush. Claudio Farina of the United Hospital in Bergamo, Italy, sent the Santa Clara team samples from 16 women with thrush whose symptoms were not caused by C. albicans . All 16 samples contained S. cerevisiae , and three contained a strain that is sold in Italy for cooking.

The risk of infection could be eliminated by stricter hygiene, Clemons says. "If you've handled bread or dough, wash your hands thoroughly afterwards," is his advice. The researchers will publish their results in the July issue of the Journal of Clinical Microbiology .

Once again, evidence is accumulating that cancers are caused by infective agents (21 August, p 5) . Although Andy Coghlan mentions the possibility that bacteria are involved, the kneejerk reaction of most cancer experts and commentators is to suggest the involvement of a virus.

This, despite the fact that for more than a century, nonviral microorganisms have been implicated in cancer. Although it is now recognised that the bacterium Helicobacter pylori is involved in gastric cancer, there is ample evidence that other nonviral microorganisms—including mycobacteria and even common bacteria such as staphylococci and yeasts such as Candida albicans —can lead to cancer.

Although much of this evidence appears in the historical literature, recent work continues to confirm that bacteria can cause cancer. While this research is largely ignored, vast amounts of time and money are spent attempting to prove the viral theory of human cancer.