
Concept explainers
Unwelcome Dinner Guests
How do harmful bacteria get into our food? Marty foodborne illnesses result from consumption of contaminated beef. The intestinal tracts of about a third or the cattle in the United States carry bacteria that are harmful to humans, and these bacteria can be transmitted to humans when a meatpacker accidentally grinds some gut contents into hamburger. Similarly, chicken feces may splash onto eggs, setting the stage for harmful bacteria to enter the eggs through tiny cracks or when the consumer breaks the egg and its contents contact the shell. Produce such as lettuce, spinach, tomatoes, and melons can also become contaminated if farm fields are exposed to animal feces, which can be deposited by deer or wandering domestic animals or carried from nearby ranches and feedlots in dust or runoff. The warm, moist environments in which sprouts are grown provide excellent growing conditions for any harmful bacteria that may have been present on the seeds from which the sprouts were produced.
How can you protect yourself from the bacteria that share our food supply? It's easy: Clean, cook, and chill. Cleaning helps prevent the spread or pathogens. Wash your hands before preparing food, and wash all utensils and cutting boards after preparing each item. Thorough cooking is the best way to ensure that any bacteria present in food are killed. Meats, in particular, must be thoroughly cooked; food safety experts recommend using a meat thermometer to ensure that the thickest part of cooked pork or ground beef has reached 16CTF. The safe temperature for cuts or beef, veal, or lamb is 145°F; for all poultry, 165°F. The color or cooked meat can be an unreliable indicator of safety, but when a meat thermometer is unavailable, try to avoid eating meat that is still pink inside, especially ground beef. Fish should be cooked until it is opaque and flakes easily with a fork; cook eggs until both white and yolk are firm. Finally, keep stored food cold. Pathogens multiply most rapidly at temperatures between 4CT and 140CF. So get your groceries home from the store and into the refrigerator or freezer as quickly as possible. Don’t leave cooked leftovers unrefrigerated for more than 2 hours. Thaw frozen foods in the refrigerator or the microwave, not at room temperature. A little bit of attention to food safety can save you from unwelcome guests in your food.
CONSIDER THIS Consumer groups contend that we can improve food safety by giving government agencies additional funding and greater authority to inspect rood processing plants and order recalls of contaminated food. Opponents or such steps argue that we need not empower government agencies because the best protection against rood contamination is informed consumers, who will stop buying products from companies that have produced unsafe foods. Would you support or oppose additional government oversight of food safety?

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Chapter 20 Solutions
Biology: Life on Earth with Physiology (11th Edition)
- There is currently a H5N1 cattle outbreak in North America. According to the CDC on Feb 26*: "A multistate outbreak of HPAI A(H5N1) bird flu in dairy cows was first reported on March 25, 2024. This is the first time that these bird flu viruses had been found in cows. In the United States, since 2022, USDA has reported HPAI A(H5N1) virus detections in more than 200 mammals." List and describe two mechanisms that could lead to this H5N1 influenza strain evolving to spread in human: Mechanisms 1: Mechanisms 2: For the mutations to results in a human epidered they would need to change how the virus interacts with the human host. In the case of mutations that may promote an epidemic, provide an example for: a protein that might incur a mutation: how the mutation would change interactions with cells in the respiratory tract (name the receptor on human cells) List two phenotypic consequence from this mutation that would increase human riskarrow_forwardYou have a bacterial strain with the CMU operon: a) As shown in the image below, the cmu operon encodes a peptide (Pep1), as well as a kinase and regulator corresponding to a two-component system. The cmu operon is activated when Pep 1 is added to the growth media. Pep1 is a peptide that when added extracellularly leads to activation of the Cmu operon. Pep1 cmu-kinase cmu-regulator You also have these genetic components in other strains: b) An alternative sigma factor, with a promoter activated by the cmu-regulator, that control a series of multiple operons that together encode a transformasome (cellular machinery for transformation). c) the gene cl (a repressor). d) the promoter X, which includes a cl binding site (and in the absence of cl is active). e) the gene gp (encoding a green fluorescence protein). Using the cmu operon as a starting point, and assuming you can perform cloning to rearrange any of these genomic features, how would you use one or more of these to modify the…arrow_forwardYou have identified a new species of a Gram-positive bacteria. You would like to screen their genome for all proteins that are covalently linked to the cell wall. You have annotated the genome, so that you identified all the promoters, operons, and genes sequences within the operons. Using these features, what would you screen for to identify a set of candidates for proteins covalently linked to the bacterial cell wall.arrow_forward
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- Biology 2eBiologyISBN:9781947172517Author:Matthew Douglas, Jung Choi, Mary Ann ClarkPublisher:OpenStaxHuman Heredity: Principles and Issues (MindTap Co...BiologyISBN:9781305251052Author:Michael CummingsPublisher:Cengage Learning
- Biology: The Dynamic Science (MindTap Course List)BiologyISBN:9781305389892Author:Peter J. Russell, Paul E. Hertz, Beverly McMillanPublisher:Cengage Learning



