miocrobiology.ppt

Microbiology;1.Introduction Microbiology is the study of microorganisms, which are unicellular or multicellular microscopic organisms. This includes eukaryotes(真核生物) such as fungi and algae(藻类) and prokaryotes(原核生物) such as bacteria. Viruses, though not strictly classed as living organisms, are also studied. Microbiology is a broad term which includes many branches like virology, mycology, parasitology and others. A person who specializes in the area of microbiology is a microbiologist.; 2. Bacteria Most bacteria (singular: bacterium) are unicellular microorganisms. They grow in soil, acidic hot springs, radioactive waste, seawater, and deep in the Earth‘s crust（地壳）. There are approximately ten times as many bacterial cells as human cells in the human body, with large numbers of bacteria on the skin and in the digestive tract. A few are beneficial, some are pathogenic（cause disease） bacteria and cause infectious diseases. ;2.1 Morphology(形态学) Bacteria display a wide diversity of shapes and sizes, called morphologies. Most bacterial species are either spherical, called cocci (sing. coccus) (球菌)or rod-shaped, called bacilli (sing. bacillus). Some rod-shaped bacteria, called vibrio（弧菌）, are slightly curved or comma-shaped; others, can be spiral-shaped, called spirilla（螺菌）.;;Escherichia coli 大肠埃希杆菌;Vibrio cholerae 霍乱弧菌;2.2 Cell structure; capsule(荚膜):protection against phagocytosis(吞噬作用) and desiccation(干燥)，help attachment of bacteria to other cells or surfaces，composed of polysaccharides and sometimes protein cell wall: prevents osmotic lysis of cell protoplast（原生质体） and confers rigidity and shape on cells. Gram-positive bacteria: peptidoglycan（肽聚糖） complexed with teichoic acids（磷壁酸） Gram-negative bacteria: peptidoglycan surrounded by phospholipid，lipoprotein and lipopolysaccharide( LPS,脂多糖) ; Plasma membrane: permeability barrier; transport of solutes; energy generation; location of numerous enzyme systems; composed of phospholipid an