Tips from the journals of the American Society for Microbiology

Scientists Uncover Vast Microbial Diversity of Carnivorous Pitcher Plant

The microbial ecosystem inside the carnivorous pitcher plant is vastly more diverse than previously thought according to research published in the March 2010 issue of the journal Applied and Environmental Microbiology.

Researchers from Louisiana State University used genomic fingerprinting technology to assess the bacterial diversity inside leaves of Sarracenia alata, commonly known as the pitcher plant. A pitcher plant is a carnivorous plant that lives in nitrogen poor soil augmenting the inadequate nitrogen by trapping and digesting insects. It has tubular shaped leaves that contain a liquid that is used for digestion. Over the past 35 years studying these plants using traditional culture-based methods, scientists have only identified 20 distinct bacteria in the pitcher.

“The microbial richness associated with the pitcher fluid from Sarracenia alata is high, with more than 1,000 phylogroups identified across at least seven phyla and over 50 families,” say the researchers, who studied 10 plants in a Louisiana wildlife management area for 5 months during the spring and summer of 2009.

The researchers noted as well that approximately a third of all the bacteria were unidentifiable. They also observed that not only were the bacterial populations distinctly different from nearby soil samples, they started out different in each plant but over time they became more similar to one another.

“These findings indicate that the bacteria associated with pitcher plant leaves are far from random assemblages and represent an important step toward understanding this unique plant-microbe interaction,” say the researchers.

(M.M. Koopman, D.M. Fuselier, S. Hird, B.C. Carstens. 2010. The carnivorous pale pitcher plant harbors diverse, distinct, and time-dependent bacterial communities. Applied and Environmental Microbiology, 76. 6: 1851-1860.)

Are Hand Sanitizers Better than Handwashing Against the Common Cold?

A new study suggests that hand sanitizers containing ethanol are much more effective at removing rhinovirus from hands than washing with soap and water. Sanitizers containing both ethanol and organic acids significantly reduced recovery of the virus from hands and rhinovirus infection up to 4 hours following application. The researchers from the University of Virginia School of Medicine, Charlottesville and Dial Corporation, Scottsdale, Arizona detail their findings in the March 2010 issue of the journal Antimicrobial Agents and Chemotherapy.

Rhinovirus is the known cause of approximately 30 to 35% of common cold cases in adults. Hand-to-hand contact is one of the main avenues of transmission contributing to the spread of rhinovirus infections. In the study researchers compared the effects of hand washing with soap and water and an ethanol-based hand sanitizer by contaminating the fingers of healthy volunteers with rhinovirus and then randomly grouping them and administering one of six hand treatments. The experiments ranged from a control group who had no treatment, several groups who washed their hands for differing amounts of time (some with soap, some without), and several who used varying amounts of hand sanitizer. Results showed that the ethanol hand sanitizer removed approximately 80% of detectable rhinovirus from hands and was much more effective than no treatment, water alone, or soap and water. Soap and water removed rhinovirus from 31% of hands.

Further, researchers added organic acids to the ethanol-based sanitizer and analyzed its ability to provide persistent antiviral activity against rhinovirus following application. Results showed that the sanitizer containing both organic acids and ethanol inactivated the virus on hands and prevented infection 2 to 4 hours following application.

“The ethanol-containing hand disinfectants were significantly more effective than hand washing with water or with soap and water for removal of detectable rhinovirus for the hands in this study,” say the researchers. “Furthermore, a formula containing organic acids and ethanol resulted in residual activity that significantly reduced virus recovery from the hands and rhinovirus infection for up to 4 hours after application.”

(R.B. Turner, J.L. Fuls, N.D. Rodgers. 2010. Effectiveness of hand sanitizers with and without organic acids for removal of rhinovirus from hands. Antimicrobial Agents and Chemotherapy, 54. 3: 1363-1364.)

Infection with Tickborne Parasite May Suppress Malaria

A new study suggests that monkeys chronically infected with babesiosis, a tick-borne parasite, are able to suppress malaria infection when exposed to a simian malaria parasite. The researchers from the Biomedical Primate Research Center, Rijswijk, The Netherlands report their findings in the March 2010 issue of the journal Infection and Immunity.

Babesia parasites are known to infect a wide variety of mammalian hosts and awareness of the role these organisms play as zoonotic agents of human disease is growing. Of the population infected with Babesia microti, 25% of adults and 50% of children remain asymptomatic. Human malaria is caused by four different Plasmodium species, however, Plasmodium falciparum and Plasmodium vivax are the most significant with P. falciparum attributed to more than 1 million deaths annually in sub-Saharan Africa.

Prior studies of Babesia and Plasmodium coinfection in rodents have reported induced cross-protection. In an attempt to confirm their prior report that a rhesus macaque chronically infected with B. microti was able to suppress infection with Plasmodium cynomolgi (a parasite of macaques with attributes similar to P. vivax), researchers infected six naive monkeys with B. microti and then 24 days later challenged four of them plus four naïve monkeys with P. cynomolgi blood-stage parasites. Results showed a significant decrease in P. cynomolgi infection in monkeys coinfected with B. microti.

“We conclude that ongoing infection with B. microti parasites leads to suppression of malaria infection,” say the researchers.

(L.M. van Duivenvoorde, A. Voorberg-van der Wel, N.M. van der Werff, G. Braskamp, E.J. Remarque, I. Kondova, C.H.M. Kocken, A.W. Thomas. 2010. Suppression of Plasmodium cynomolgi in rhesus macaques by coinfection with Babesia microti. Infection and Immunity, 78. 3: 1032-1039.)

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