Unit Overview – pages Viruses, Bacteria, Protists, and Fungi Viruses and Bacteria Bacteria

Section 18.2 Summary – pages What is bacterium? A bacterium consists of a very small cell. Although tiny, a bacterial cell has all the structures necessary to carry out its life functions.

Section 18.2 Summary – pages A Typical Bacterial Cell Capsule Cell Wall Chromosome Flagellum Plasmid Pilus Plasma membrane

Section 18.2 Summary – pages The structure of bacteria A bacterial cell remains intact as long as its cell wall is intact. If the cell wall is damaged, water will enter the cell by osmosis, causing the cell to burst. Scientists used a bacterium’s need for an intact cell wall to develop a weapon against bacteria that cause disease.

Section 18.2 Summary – pages The structure of bacteria In 1928, Sir Alexander Fleming accidentally discovered penicillin,

Section 18.2 Summary – pages The structure of bacteria Later, biologists discovered that penicillin can interfere with the ability of some bacteria to make cell walls. When such bacteria grow in penicillin, holes develop in their cell walls, water enters their cells, and they rupture and die.

Section 18.2 Summary – pages Prokaryotes and Eukaryotes Diversity of Bacteria 2 Kingdoms: archaebacteria and eubacteria. used to be one kingdom:Monera

Section 18.2 Summary – pages Diversity of Bacteria: Eubacteria Eubacteria have peptidoglycan (a kind of sugar) in their cell walls and Archaebacteria do not. live almost everywhere and use organic molecules as their food source.

Section 18.2 Summary – pages Eubacteria can be: Parasites- obtaining their nutrientsfrom living organisms. Eubacteria: The heterotrophs Saprophytes - organisms that feed on dead organisms or organic wastes.

Chemosynthetic autotroph - energy in inorganic compounds containing sulfur and nitrogen photosynthetic autotroph - need light to make the organic molecules that are their food.

Section 18.2 Summary – pages types: archaebacteria: Archaebacteria: The extremists One lives in oxygen-free environments and produces methane gas. marshes, lake sediments, sewage plants and the digestive tracts of some mammals, such as cows.

Section 18.2 Summary – pages A second: lives only in water with high concentrations of salt. Archaebacteria: The extremists Dead Sea

Section 18.2 Summary – pages A third: lives in the hot, acidic waters of sulfur springs and cracks in the deep ocean. Archaebacteria: The extremists

Section 18.2 Summary – pages Identifying bacteria Gram stain technique that distinguishes two groups of bacteria because the stain reflects a basic difference in the composition of bacterial cell walls.

Section 18.2 Summary – pages Gram-positive bacteria are purple Gram-negative bacteria are pink. Gram-positive bacteria Gram-negative bacteria Identifying bacteria

Section 18.2 Summary – pages Each are affected by different antibiotics Gram-positive bacteria Gram-negative bacteria Identifying bacteria

Section 18.2 Summary – pages Identifying bacteria Bacterial cell walls also give bacteria different shapes. Shape is another way to categorize bacteria. Coccus—spheres Bacillus—rods Spirillum–spirals

Section 18.2 Summary – pages Identifying bacteria Bacterial cells grow in patterns that provide another way of categorizing them. Diplo–grows in pairs. Staphylo–grows in clusters that resemble grapes. Strepto–grows in chains of cells.

Section 18.2 Summary – pages Reproduction Binary fission: a process in which one cell divides to form two identical cells Binary fission is a form of asexual reproduction (involves only one parent).

Section 18.2 Summary – pages Reproduction Conjugation: one bacterium transfers all or part of its chromosome to another cell through or on a pilus that connects the two cells. sexual reproduction involving two parents Results in new genetic composition

Section 18.2 Summary – pages Diversity of metabolism Modern bacteria have diverse types of respiration. Obligate aerobes: require oxygen for respiration Obligate anaerobes: are killed by oxygen

Section 18.2 Summary – pages A survival mechanism Some bacteria, when faced with unfavorable environmental conditions, produce endospores. Endospore: a tiny structure that contains a small amount of bacterium’s DNA and cytoplasm, encased by a tough outer covering that resists drying out, temperature extremes, and harsh chemicals.

Section 18.2 Summary – pages A survival mechanism To kill endospores, items must be sterilized—heated under high pressure in either a pressure cooker or an autoclave.

Section 18.2 Summary – pages A survival mechanism This is because the endospores of the bacterium called Clostridium botulinum easily get into foods being canned. Canned food must be sterilized and acidified.

Section 18.2 Summary – pages A survival mechanism Bacteria grow in the anaerobic environment of the can and produce a powerful deadly poison, called a toxin, as they grow. This deadly toxin saturates the food and, if eaten, causes the disease called botulism.

Section 18.2 Summary – pages A survival mechanism B. anthracis causes anthrax, a disease that commonly infects cattle and sheep, but can also infect humans. A different bacterium, Bacillus anthracis, lives in the soil. Most human anthrax infections are fairly harmless and occur on the skin as a result of handling animals.

Section 18.2 Summary – pages The Importance of Bacteria Bacteria help to fertilize fields, to recycle nutrients on Earth, and to produce foods and medicines. Disease-causing bacteria are few compared with the number of harmless and beneficial bacteria on Earth.

Section 18.2 Summary – pages The Importance of Bacteria Nitrogen fixation: process in which some species of bacteria convert N 2 into ammonia (NH 3 ) Bacteria are the only organisms that can perform these chemical changes.

Section 18.2 Summary – pages Nitrogen fixation Farmers grow legume crops after the harvesting of crops such as corn, which depletes the soil of nitrogen. Some nitrogen- fixing bacteria live symbiotically within the roots of some trees and legumes.

Section 18.2 Summary – pages Recycling of nutrients Autotrophic bacteria can be food that is passed from one heterotroph to the next in the food chain/web – primary producers In the process of making food, many autotrophs aid in replenishing the supply of oxygen in the atmosphere.

Section 18.2 Summary – pages Food and medicines Some foods that you eat—Swiss cheese, crispy pickles, tangy yogurt, vinegar, and sauerkraut. Inhabit your intestines and produce vitamins and enzymes that help digest food. Antibiotics