New Family Of Antibacterial Agents Uncovered

As bacteria resistant to commonly used antibiotics continue to increase in number, scientists keep searching for new sources of drugs. One potential new bactericide has now been found in the tiny freshwater animal Hydra.

The protein identified by Joachim Grötzinger, Thomas Bosch and colleagues at the University of Kiel, hydramacin-1, is unusual (and also clinically valuable) as it shares virtually no similarity with any other known antibacterial proteins except for two antimicrobials found in another ancient animal, the leech.

Hydramacin proved to be extremely effective though; in a series of laboratory experiments, this protein could kill a wide range of both Gram-positive and Gram-negative bacteria, including clinically-isolated drug-resistant strains like Klebsiella oxytoca (a common cause of nosocomial infections). Hydramacin works by sticking to the bacterial surface, promoting the clumping of nearby bacteria, then disrupting the bacterial membrane.

Grötzinger and his team also determined the 3-D shape of hydramacin-1, which revealed that it most closely resembled a superfamily of proteins found in scorpion venom; within this large group, they propose that hydramacin and the two leech proteins are members of a newly designated family called the macins.

New Research Lights Up Chronic Bacterial Infection Inside Bone

A new report demonstrates how a sensitive imaging technique gives scientists the upper hand in seeking out bacteria in chronic infections.Listeria monocytogenes is a type of pathogenic bacteria that can cause severe illness and death. Listeria outbreaks recently claimed twenty lives in Canada. Additionally, Listeria infection is the third most common cause of bacterial meningitis in newborns, and can cause abortion and stillbirth. When the infection is caught in time, treatment can be difficult and take weeks to clear with intravenous administration of antibiotics.

Therefore, in order to understand how this pathogen can be so elusive and difficult to treat, a research team from Stanford University School of Medicine studied mice infected with Listeria. Their report describes how they use a technique called in vivo bioluminescence to light up bacteria and allow them to see extremely tiny amounts of bacterial cells in living animals. Using this method, they found that small persistent patches of Listeria took up residence inside bone marrow in the mice. This is significant because it is thought that the bone marrow can act as a reservoir to the brain and spinal cord, potentially causing life-threatening infections, such as in bacterial meningitis in newborns.

Another interesting aspect of this study is due to the use of specially designed Listeria stains in treating cancer. Clinical trials are currently underway in which non-disease-causing strains of Listeria are administered to cancer patients to generate immune responses against tumors. The researchers thus also looked at these attenuated strains, and found that they too could be harbored in bone marrow. It is still unclear, however, if such bacterial persistence will increase or decrease therapeutic effects.

The report was written by Jonathan Hardy, Pauline Chu, and Christopher H. Contag of the Stanford University School of Medicine in California. The report is published in the January/February issue of a new research journal, Disease Models & Mechanisms (DMM), published by The Company of Biologists, a non-profit based in Cambridge, UK.

Women's Brains Recognize, Encode Smell Of Male Sexual Sweat

A new Rice University study published in the Journal of Neuroscience found that socioemotional meanings, including sexual ones, are conveyed in human sweat.

Denise Chen, assistant professor of psychology at Rice, looked at how the brains of female volunteers processed and encoded the smell of sexual sweat from men. The results of the experiment indicated the brain recognizes chemosensory communication, including human sexual sweat.

Scientists have long known that animals use scent to communicate.

Chen's study represents an effort to expand knowledge of how humans’ sense of smell complement their more powerful senses of sight and hearing.

The experiment directly studied natural human sexual sweat using functional magnetic resonance imaging (fMRI). Nineteen healthy female subjects inhaled olfactory stimuli from four sources, one of which was sweat gathered from sexually aroused males.

The research showed that several parts of the brain are involved in processing the emotional value of the olfactory information. These include the right fusiform region, the right orbitofrontal cortex and the right hypothalamus.

"With the exception of the hypothalamus, neither the orbitofrontal cortex nor the fusiform region is considered to be associated with sexual motivation and behavior," Chen said. "Our results imply that the chemosensory information from natural human sexual sweat is encoded more holistically in the brain rather than specifically for its sexual quality."

Humans are evolved to respond to salient socioemotional information.

Distinctive neural mechanisms underlie the processing of emotions in facial and vocal expressions. The findings help explain the neural mechanism for human social chemosignals.

The understanding of human smell at the neural level is still at the beginning stage. The present work is the first fMRI study of human social chemosignals.

The research, co-authored by Chen and Wen Zhou, graduate student in the Psychology Department, appeared in the December 31 issue of Journal of Neuroscience.

The research was supported in part by the National Institutes of Health.