News From The Journals Of The American Society For Microbiology: February 2012
Italy is well-known for aesthetics that play to every sense of the human sensory system: automotive style, espresso, ancient architecture, music, and Fettuccini Alfredo, among much else. Now a team of Italian investigators has analyzed the microbiota of 19 sourdoughs used in traditional Italian breads. They report their findings in the February issue of the journal Applied and Environmental Microbiology.
"We found a large diversity of mainly lactic acid bacteria among the sourdoughs," says principal investigator Marco Gobbetti. "We related such differences to the environmental parameters and the type of flour used; and such microbial diversity should be considered a sort of fingerprint for the uniqueness of each sourdough."
The research began with the notion of building an Italian sourdough library, wherein all things relating to sourdough - characterizing strains, typical protocols, photos of the bread, etc. - would be available, says Gobbetti. The working hypothesis: "behind the different and non-reproduceable features of each bread, there is a microbial consortium that promotes that uniqueness," says Gobbetti. New techniques in biotechnology made possible this analysis, he says.
Some notable findings: the ratio of individual lactic acid bacteria to yeast cells varied from 100:1 to 10:1, "which is common for sourdoughs," says Gobbetti. Two outliers were Pane di Matera, and Pane Casareccio di Genzano, with ratios of 1000:1 and 1:1, respectively. The number of strains of lactic acid bacteria varied from 5-17. The number of species of lactic acid bacteria also varied widely among the sourdoughs. Greater diversity of both strains and species probably correlates with a more typical sourdough taste, says Gobbetti.
The investigators note that free amino acids and gamma amino butyric acid (GABA), products of lactic acid bacteria, may increase a sourdough's nutritional value. In particular, "the amount of GABA in 150 g. of Pane di Matera PGI represents the minimum effective daily dose to achieve a lowering of blood pressure in mild hypertensives," says Gobbetti.
Interestingly, specific lactic acid bacteria are often characteristic of sourdoughs from a specific region, according to the report. But these are subject to change. Several years ago, when Pane di Altamura PDO sourdough was characterized, Lactobacillus plantarum was found to be the dominant species. This time, Wickerhamomyces cibaria and W. confusa predominated. Several factors may influence such change, "especially... instability of the sourdough microbiotas during daily back slopping as affected by the type of flour and related autochthonous [lactic acid bacteria]," according to the report. "Indeed, a stable microbiota over a long period of time has been described only in a few sourdoughs that are used as the sole leavening agent." (Back slopping refers to the procedure for renewing or refreshing the sourdough by taking part of the fermented dough to inoculate new flour and water.)
"The results of this study could be helpful to choose specific starter cultures," the researchers conclude. "This should guarantee a high reproducibility of the quality characterizing the traditional and/or typical breads."
(F. Minervini, R. Di Cagno, A. Lattanzi, M. De Angelis, L. Antonielli, G. Cardinali, S. Cappelle, and M. Gobbetti, 2012. Lactic acid bacterium and yeast microbiotas of 19 sourdoughs used for traditional/typical Italian breads: interactions between ingredients and microbial species diversity. Appl. Environ. Microbiol. 78:1251-1264.)
Copper Iodide Nanoparticles Effective Against 2009 Pandemic H1N1 Influenza Virus
Copper-iodide nanoparticles have long-lasting antiviral activity against the 2009 pandemic H1N1 influenza virus, according to a paper in the February issue of the journal Applied and Environmental Microbiology.
The copper iodide generates reactive oxygen species which kill viruses by degrading viral proteins. The particles can be applied to products such as filters, face masks, kitchen cloths, counter tops, and other products where people might come into contact with virus particles, says first author Yoshie Fujimori of NBC Meshtec, Inc., Tokyo, Japan. This is the first demonstration of antiviral activity in copper-iodide nanoparticles.
"Copper-iodide has antiviral activity against other viruses, and antibacterial activity as well," says Fujimori. "We have already sold some products, such as face masks, disposable protective clothing, antiviral sheets and blankets, and bannisters."
Copper has long been known to have antibacterial activity, and several copper compounds had previously been found to have antiviral activity, against both avian influenza virus and human immunodeficiency virus. But the colors of copper metal and copper oxide would have altered the appearance of any products to which they might be applied, while the white copper iodide nanoparticles would not have done so, says Fujimori.
Copper iodide nanoparticles are stable in air and water, which accounts for their long-lasting antiviral activity, whereas the commonly used alcohol hand-sanitizers are relatively ineffective against viruses.
The researchers showed that copper-iodide degrades functional proteins, and they suspect that it does so by generating so-called reactive oxygen species, which are known to degrade proteins. A major advantage of this mechanism is that it would be extremely difficult for a virus to develop resistance to this mechanism, says Fujimori.
(Y. Fujimori, T. Sato, T. Hayata, T. Nagao, M. Nakayama, T. Nakayama, R. Sugamata, and K. Suzuki, 2012. Novel antiviral characteristics of nanosized copper(I) iodide particles showing inactivation activity against 2009 pandemic H1N1 influenza virus. Appl. Environ. Microbiol. 78:951-955.)
Breakdown of Triglycerides in Heart Muscle Boosts Cardiac Function
The heart relies heavily on oxidation of fatty acids for energy production. However, excess storage of fatty acids as triglycerides, within heart muscle cells, frequently observed in patients with obesity and diabetes, is often associated with cardiac dysfunction. The question remained: was this cause and effect? Now a team of investigators shows that baseline heart function "showed moderate, but significant improvement" in mouse models that overproduce an enzyme that breaks down these triglycerides, says principal investigator Jason Dyck, of the University of Alberta, Edmonton. The research is published in the February Molecular and Cellular Biology.
The investigators showed further that mice that overproduce the enzyme "were able to run 20% longer than the controls when subjected to a treadmill test," says first author Petra Kienesberger, of the University of Alberta.
Then, in experiments in which mouse models were surgically constructed to mimic hypertension, the researchers showed that "overproduction of the enzyme protects from the development of cardiac/contractile dysfunction under this pathological condition," says Kienesberger.
"Together, these data demonstrate for the first time that decreased myocardial triglyceride accumulation plays a role in regulating cardiac function at baseline as well as an important protective role in preventing cardiac dysfunction in response to a severe pressure overload, as observed with hypertension," says Dyck.
"These findings are highly relevant to basic and clinical research," says Kienesberger. "They suggest that regulation of cardiac triglyceride content and breakdown plays a central role in mediating cardiac function, and that pharmacological modification of cardiac [enzymatic] activity [to break down triglyceride] could be used as therapy to improve contractile function of the diseased heart. However, it remains to be tested whether reducing triglycerides is also beneficial in obesity and diabetes. This concept... opens new avenues of research not previously identified."
The research was enabled only recently by new genetic tools that specifically target cardiac triglycerides and by a novel mouse model, in which triglyceride could be reduced by boosting the enzyme responsible for breaking it down, says Kienesberger.
(P.C. Kienesberger, T. Pulinilkunnil, M.M.Y. Sung, J. Nagendran, G. Haemmerle, E.E. Kershaw, M.E. Young, P.E. Light, G.Y. Oudit, R. Zechner, and J.R.B. Dyck, 2012. Myocardial ATGL overexpression decreases the reliance on fatty acid oxidation and protects against pressure overload-induced cardiac dysfunction. Mol. Cell. Biol. 32:740-750.)
Androgen enhances replication of hepatitis B virus (HBV), rendering males more vulnerable than females to this virus, according to research published in the February Journal of Virology.
"Our studies allowed us to understand the gender disparity of HBV carriers, and why this virus tends to cause more severe liver disease in men than in women," says principal investigator James Ou of the University of Southern California.
The researchers found no difference between levels of virus in prepubescent male and female mice. However, post-puberty, levels in males exceeded those in females, in some cases by more than double, says Ou. Subsequently castrating male mice reduced the viral load, but injecting castrated mice with an androgen agonist resulted in a rising viral load again.
In a third set of experiments, the researchers removed the androgen receptor by genetic knockout, once again abolishing the androgen's effect on hepatitis B replication. Then they drilled down still further, discovering elements within the HBV genome which are recognized by the host's activated androgen receptor, which then boosts viral gene expression and replication.
Epidemiologic studies have shown that men are three to seven times more likely than women to become HBV carriers, and male HBV carriers are more likely to develop cancer of the liver (hepatocellular carcinoma) than female carriers.
"Hepatitis B virus is one of the most important human pathogens," says Ou. "Approximately 350 million people worldwide are chronically infected, and roughly one million die annually."
HBV can be transmitted sexually, as well as via non-sterile needles, and perinatally. In areas where the virus is endemic, it is frequently transmitted among young children. It is present in blood (including menstrual blood), vaginal secretions, saliva, semen, breast milk, and to a lesser extent in other bodily fluids. A vaccine is available for HBV.
(Y. Tian, C.f. Kuo, W.-l. Chen, and J.-h.J. Ou, 2012. Enhancement of hepatitis B virus replication by androgen and its receptor in mice. J. Virol. 86:1904-1910.)