The bacterial cell wall is a rigid wall that protects the underlying cell

The bacterial cell wall is a rigid wall that protects

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The bacterial cell wall is a rigid wall that protects the underlying cell membrane from bursting. If the cell wall is damaged, the cell membrane of the bacterium bursts, killing the bacterium. Penicillin prevents cell wall synthesis in the bacterium, causing the cell membrane to burst and the bacterium to die. Because human cells do not have a cell wall, they are not damaged by penicillin Spores enable the bacteria to exist in a “sleepy,” or dormant, state until conditions improve. Rickettsia and chlamydia are classified as bacteria(they are smaller than most bacteria and must reproduce within the living cells of a host). Because they require a living host, they are called parasites . The rickettsiae are often carried by fleas, ticks, and body lice. For example, the rickettsia that causes Rocky Mountain spotted fever is carried by the tick. Body lice carry the rickettsia responsible for epidemic typhus. Chlamydial infection is also responsible for trachoma, a serious eye infection that is a leading cause of blindness in the world. Like other bacterial infections, rickettsial and chlamydial infections are treated with antibiotics. Viruses are the smallest of the infectious agents. They are not cells and consist of either ribonucleic acid (RNA) or deoxyribonucleic acid (DNA) surrounded by a protein shell. Because viruses can only reproduce within the living cells of a host, they are parasites. Fungus is a plantlike organism, such as a mushroom, that grows best in dark, damp places. Yeasts and molds are types of fungi. Pathogenic fungi cause mycotic infections. Mycotic infections are usually localized and include athlete’s foot, ringworm, thrush, and vaginitis. Candida albicans is a yeastlike fungus that normally inhabits the mouth, digestive tract, and vagina. When Candida overgrows, it can cause an infection in the mouth (thrush), intestinal symptoms, or vaginitis. Protozoa are single-celled, animal-like microbes. The four main types of protozoa are amebas, ciliates, flagellates and sporozoa . Protozoa are found in the soil and in most bodies of water. Amebic dysentery and giardiasis are caused by protozoan parasites. The parasites are ingested in contaminated water and food and cause severe diarrhea. Malaria is caused by a sporozoan called a plasmodium. Plasmodium malariae is carried by a mosquito, which is capable of spreading malaria over a wide region.
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Other (Multicellular) Disease-Causing Organisms Parasitic worms, called helminths , are multicellular animals that are parasitic and pathogenic to humans. Roundworms include ascarides, pinworms, hookworms, trichinae, and the tiny worms that cause filariasis or elephantiasis. Infestation by pinworms is common in children and is very hard to control. The pinworms live in the intestinal tract but lay their eggs on the outer perianal area. The deposition of the eggs causes itching (pruritus). Trichinosis is transmitted by ingestion of undercooked, contaminated pork; and filariasis is transmitted by biting insects.
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