Many bacterial pathogens and symbionts utilize type III secretion systems to deliver bacterial effector proteins into host cells. These effector proteins have the capacity to modulate a large variety of cellular functions in a highly regulated manner. Here, we report that the phosphoinositide phosphatase SopB, a Salmonella Typhimurium type III secreted effector protein, diversifies its function by localizing to different cellular compartments in a ubiquitin-dependent manner. We show that SopB utilizes the same enzymatic activity to modulate actin-mediated bacterial internalization and Akt activation at the plasma membrane and vesicular trafficking and intracellular bacterial replication at the phagosome. Thus, by exploiting the host cellular machinery, Salmonella Typhimurium has evolved the capacity to broaden the functional repertoire of a virulence factor to maximize its ability to modulate cellular functions.

Virulence effectors delivered into intestinal epithelial cells by Salmonella trigger actin remodeling to direct pathogen internalization and intracellular replication in Salmonella-containing vacuoles (SCVs). One such effector, SptP, functions early during pathogen entry to deactivate Rho GTPases and reverse pathogen-induced cytoskeletal changes following uptake. SptP also harbors a C-terminal protein tyrosine phosphatase (PTPase) domain with no clear host substrates. Investigating SptP's longevity in infected cells, we uncover a late function of SptP, showing that it associates with SCVs, and its PTPase activity increases pathogen replication. Direct SptP binding and specific dephosphorylation of the AAA+ ATPase valosin-containing protein (VCP/p97), a facilitator of cellular membrane fusion and protein degradation, enhanced pathogen replication in SCVs. VCP and its adaptors p47 and Ufd1 were necessary for generating Salmonella-induced filaments on SCVs, a membrane fusion event characteristic of the pathogen replicative phase. Thus, Salmonella regulates the biogenesis of an intracellular niche through SptP-mediated dephosphorylation of VCP.

A single crafty protein allows the deadly bacterium Salmonella enterica to both invade cells lining the intestine and hijack cellular functions to avoid destruction, Yale researchers report in the April 17 issue of the journal Cell. This evolutionary slight-of-hand sheds new insights into the lethal tricks of Salmonella, which kills more than 2 million people a year. "In evolutionary terms, this hijacking of cellular machinery to diversify the function of a bacterial protein is mind boggling,'' said Jorge Galan, senior author of the paper and the Lucille P. Markey Professor of Microbial Pathogenesis and Cell Biology and chair of microbial pathogenesis at Yale. Salmonella causes disease when it takes control of cells lining the intestinal track using its own specialized "nano-syringe" called a type III secretion system. Using this structure, Salmonella injects bacterial proteins that mimic proteins of the host cell and help the pathogen avoid destruction. The Yale study describes the crucial role a bacterial protein called SopB plays in both Salmonella's forced entry into the cell and its subsequent internal camouflage act. First, SopB works within the external membrane of the cell, called the plasma membrane, to coax the cell into taking in the pathogen, which is then encapsulated within a tiny bubble-like compartment called a vesicle. SopB's second trick helps prevent the vesicle from being sucked into the lyosome, the organelle within the cell that degrades proteins. In order to accomplish this, SopB must move from the plasma membrane of the cell to the membrane of the internal vesicle containing the pathogen. The Yale group found that Salmonella coaxes the cell to "mark" the SopB protein with a tag called ubiquitin. Addition of this tag makes the bacterial protein recognizable to the cellular machinery that normally moves proteins from the plasma membranes to internal vesicles.

While consumers are increasing demand for pork produced without antibiotics, more of the pigs raised in such conditions carry bacteria and parasites associated with food-borne illnesses, according to a new study. A comparison of swine raised in antibiotic-free and conventional pork production settings revealed that pigs raised outdoors without antibiotics had higher rates of three food-borne pathogens than did pigs on conventional farms, which remain indoors and receive preventive doses of antimicrobial drugs. "Animal-friendly, outdoor farms tend to have a higher occurrence of Salmonella, as well as higher rates of parasitic disease," said lead study author Wondwossen Gebreyes, associate professor of veterinary preventive medicine at Ohio State University. More than half of the pigs on antibiotic-free farms tested positive for Salmonella, compared to 39 percent of conventionally raised pigs infected with the bacterial pathogen. The presence of the Toxoplasma gondii parasite was detected in 6.8 percent of antibiotic-free pigs, compared to 1.1 percent of conventionally raised pigs. And two naturally raised pigs of the total 616 sampled tested positive for Trichinella spiralis, a parasite considered virtually eradicated from conventional U.S. pork operations.

Efforts to reduce the number of food-borne illnesses in the United States have stalled in the past three years, and some illnesses are on the upswing, giving new urgency to efforts to reform the nation's food safety system, the Centers for Disease Control and Prevention reported yesterday. "We need greater effort at all stages of movement of food in the food chain from farm to table" to prevent bacterial contamination, said Robert Tauxe, deputy director of the CDC's Division of Foodborne, Bacterial and Mycotic Diseases. Several factors are fueling the trend, including the intricacy of the U.S. food chain, the changing nature of the contaminating bacteria and the rise in imported food, Tauxe said. Bacteria that used to be associated mainly with meats and poultry have recently shown up in fresh produce, posing new risks, he said. Examples include E. coli 0157 in spinach and salmonella in peanuts and pistachios. "It reflects the complexity of the problem, with many different foods becoming potentially contaminated, including more fresh produce. It reflects that fact that pathogens like E. coli 0157 and salmonella can spread in the environment and contaminate a number of different foods, some of which we have not seen in the past," Tauxe said. "And the food industry is also complicated and changing, with a variety of different arenas and components from all over the world."

IS free-range pork better and safer to eat than conventional pork? Many consumers think so. The well-publicized horrors of intensive pig farming have fostered the widespread assumption that, as one purveyor of free-range meats put it, “the health benefits are indisputable.” However, as yet another reminder that culinary wisdom is never conventional, scientists have found that free-range pork can be more likely than caged pork to carry dangerous bacteria and parasites. It’s not only pistachios and 50-pound tubs of peanut paste that have been infected with salmonella but also 500-pound pigs allowed to root and to roam pastures happily before butting heads with a bolt gun. The study published in the journal Foodborne Pathogens and Disease that brought these findings to light last year sampled more than 600 pigs in North Carolina, Ohio and Wisconsin. It discovered not only higher rates of salmonella in free-range pigs (54 percent versus 39 percent) but also greater levels of the pathogen toxoplasma (6.8 percent versus 1.1 percent) and, most alarming, two free-range pigs that carried the parasite trichina (as opposed to zero for confined pigs). For many years, the pork industry has been assuring cooks that a little pink in the pork is fine. Trichinosis, which can be deadly, was assumed to be history.

Kraft Foods had been bedeviled with positive salmonella tests in products containing pistachios for months prior to its recall last week of a pistachio-laden trail mix, the company said Friday. Shortly after pistachios bound for its Back to Nature trail mix tested positive for salmonella, Kraft voluntarily recalled the product and informed the Food and Drug Administration. Earlier this week, regulators urged consumers to avoid eating pistachio-based products, the latest in a series of salmonella scares. The FDA also said that Kraft's pistachio supplier, California-based Setton Pistachio of Terra Bella Inc., the nation's second-largest pistachio processor, was voluntarily recalling its 2008 crop. A batch of Setton's pistachios had tested positive for salmonella at Skokie-based Georgia Nut Co., which makes Back to Nature trail mix for Northfield-based Kraft. That wasn't the first time Georgia Nut had discovered a positive salmonella test in conjunction with Back to Nature mix. In September, November and February, trail mix containing pistachios tested positive for salmonella, said Laurie Guzzinati, a Kraft spokeswoman.

California's pistachio growers are bracing for what could be a serious and long-lasting drop in sales as federal officials continue to advise consumers to avoid eating the nuts amid a salmonella scare. Although pistachios from only one processor -- Setton Pistachio in Terra Bella -- were found to have salmonella, California's entire $540 million pistachio industry could face the consequences. And if past experience is any indication, consumers might be slow to return. Last summer, for example, a salmonella outbreak made 1,400 people sick in 43 states, and initially tomatoes got the blame. Later the outbreak was traced to jalapeños and serrano peppers, but the tomato industry still hasn't fully recovered. Indeed, an outbreak of food-borne illness is one of the agriculture industry's worst nightmares. The health risks are high -- and the costs can reach into the millions of dollars.

A California food processing plant is voluntarily recalling up to 1 million pounds of roasted pistachio products that may have been contaminated with salmonella, the Food and Drug Administration announced Monday. The nuts came from Setton Farms in Terra Bella, California, about 75 miles south of Fresno. They were largely distributed in 2,000-pound containers to food wholesalers who would then package them for resale or incorporate them as ingredients in other products, such as ice cream and trail mix.