Kingdom Archaebacteria & Kingdom Eubacteria Chapter 24

Evolution & Classification Section 24-1

Evolution & Classification Bacteria are microscopic prokaryotes, organisms that lack a cell nucleus Unlike most organisms, bacteria have few morphological differences

Characteristics of Prokaryotes Do NOT have a membrane-bound nucleus Do have a cell membrane, but do NOT have membrane bound organelles Have ribosomes that are different from those of eukaryotes Smaller than the smallest eukaryotes Unicellular

Kingdoms of Bacteria There are two kingdoms of bacteria separated based on the ribosomal RNA sequences. Kingdom Archeabacteria – the “ancient” bacteria that live in very harsh environments Kingdom Eubacteria – the “true” bacteria that we consider to be germs

Kingdom Archaebacteria Do not have peptidoglycan, a protein-carbohydrate found in the cell walls of eubacteria Live in extreme environments so that is how they are classified

Phylum Methanogens Live in anaerobic, oxygen free environments Produce methane gas by converting H2 and CO2 into CH4, this is a form of chemosynthesis Live in swamps, sewage, marshes, animal digestive tracts.

Phylum Thermoacidophiles Can live in water that is extremely hot and acidic Found in hot springs or hydrothermal vents Use the heat and acids of their habitat to produce food by chemosynthesis

Phylum Extreme Halophiles Live in extremely salty conditions Found in the Great Salt Lake of Utah, Dead Sea, and Chaplin Lake Use the salt in their environment for energy, a form of chemosynthesis.

Kingdom Eubacteria Have peptidoglycan in their cell walls Classified on shape Classified on how they react to Gram staining

Eubacteria Shapes Eubacteria have three different shapes Bacilli – rod shaped Cocci – sphere shaped Spirilla – spiral shaped

Gram Staining A staining technique that divides bacteria into gram-positive and gram-negative The technique involves staining bacteria with a purple dye and iodine and rinsing with alcohol then restained with a pink dye

Gram Positive If the cell retains the purple color they are gram-positive and they have a thick peptidoglycan layer in their cell wall They are usually beneficial We usually use them to make antibiotics, which kill other gram-positive bacteria

Gram Negative If the cell does not retain the purple dye but takes on the pink dye it is gram-negative They have an extra layer of lipid on the outside of the cell wall They tend to resist antibiotics

Phylum Cyanobacteria They are gram-negative bacteria They perform photosynthesis and release oxygen so they are aerobic Grow in long filaments of cells Some have heterocysts, special cells that contain enzymes that can fix atmospheric nitrogen

Phylum Spirochetes Gram-negative bacteria Spiral shaped heterotrophic bacteria Most are aerobic but some are anaerobic Move by corkscrew rotation

Phylum Gram-positive Most are gram-positive to Gram stain They are found in diseases and food materials They can be filamentous or single celled

Phylum Proteobacteria The largest and most diverse phylum There are three subphylums Enteric Chemoautotrophic Nitrogen-fixing

Enteric Bacteria Gram-negative heterotrophic bacteria Inhabit intestinal tracts Live in aerobic and anaerobic conditions

Chemoautotrophs Gram-negative bacteria Extract energy from oxidizing minerals so by chemosynthesis

Nitrogen-fixing Gram-negative bacteria Usually grow symbiotically in root nodules of plants Able to convert atmospheric nitrogen into useful compounds such as ammonia and nitrates Need them to build amino acids for the building of proteins

Biology of Bacteria Section 24-2

Bacteria Structure Bacteria are typically composed of Cell wall Cell membrane Cytoplasm with ribosomes Chromosome

(a) Cell Wall Eubacteria cell walls are made of peptidoglycan Archeabacteria cell walls are composed of a different compound related to cellulose and chitin

(b) Cell Membrane The cell membrane is composed of a lipid bilayer The cell membrane has special enzymes for carrying out cellular respiration and photosynthesis The membrane of photosynthetic bacteria have folds called thylakoids like those in chloroplasts

(c) Cytoplasm Bacterial cells do not have membrane bound organelles The cytoplasm of bacterial cells is made of a viscous solution of ribosomes and DNA

(d) Capsule Many bacteria have an outer covering called a capsule The capsule is made of polysaccharides that cling to the surface of the cell and protect it against drying out or harsh chemicals When a capsule consists of a fuzzy coat of sticky sugars, it is called a glycocalyx The glycocalyx enables the bacteria to attach to the surface of host cells and tissues

(e) Pili Pili are short, hairlike protein structures found on the surface of some species of bacteria Pili help bacteria hold on to host cells and are also used for transfer of genetic material from one bacterium to another

(f) Endospores When living conditions for the bacterium become unfavourable, some bacteria form special, dehydrated cells called endospores Endospores consist of a thick outer covering that surrounds the cell’s DNA When conditions become favorable the endospores break open and produce new bacterial cells

(g) Flagella Many bacteria use flagella, whiplike structures that are used for movement Those that do not have flagella use slime to glide through or a corkscrew rotation

Nutrition of Bacteria Most bacteria are heterotrophs, they get their energy by consuming organic matter as a source of nutrition Heterotrophs that feed on dead or decaying material are called saprophytes

Nutrition of Bacteria Some bacteria are autotrophs, organisms capable of creating their own food energy Photosynthetic – use sunlight to create food energy Chemosynthetic – use the energy from oxidizing inorganic compounds to create food energy

Respiration in Bacteria The type of cellular respiration is another difference between bacteria groups Organisms that use oxygen during cellular respiration are aerobes. Organisms that do not use oxygen during cellular respiration are anaerobes

Respiration in Bacteria The presence or absence of oxygen in the environment is one way to distinguish between different bacteria Bacteria called obligate aerobes cannot live without oxygen Bacteria called obligate anaerobes cannot live in the presence of oxygen Bacteria called facultative anaerobes can use oxygen when it is available but they do not depend on it

Reproduction in Bacteria Most bacteria reproduce by binary fission, a process in which the chromosome replicates then the cell divides Binary fission is a type of asexual reproduction

Genetic Recombination in Bacteria Genetic recombination is a nonreproductive means by which bacteria acquire new combinations of genes There are three special ways that bacteria exchange genes

Conjugation The process of exchanging genetic material through cell to cell contact by a conjugation bridge from the pili During conjugation DNA moves from one bacterium to another.

Transformation The process by which bacteria cells pick up and incorporate DNA from dead bacteria cells. They take up DNA from dead cells of the same or closely related species.

Transduction The process by which the transfer of DNA from one bacteria to another is done by viruses. Viruses called bacteriophages are used to carry DNA between cells

Bacteria and Humans Section 24-3

Bacteria and Disease The scientific study of disease is called pathology. Bacteria that cause disease are called pathogens. Some bacteria cause disease by producing toxins Exotoxins are toxins that are secreted into the environment by the bacterium Endotoxins are toxins are toxins that are released once the bacterium dies

Antibiotics Antibiotics are drugs that fight bacteria by interfering with their cellular functions. Many antibiotics are able to affect a wide variety of organisms, they are called broad spectrum antibiotics

Antibiotic Resistance When a population of bacteria is exposed to an antibiotic, the most susceptible die. A few mutant bacteria are resistant to the antibiotic and continue to grow. A resistant population then grows from these mutant bacteria and these new populations are antibiotic resistant This results from over use of antibiotics.

Useful Bacteria Bacteria are used in sewage treatment, and as decomposers, breaking down the remains of organic matter in dead plant and animal wastes. They are recyclers the return nutrients back to the environment.

Useful Bacteria Bacteria are useful in food production. Bacteria help us make buttermilk, sour cream, yogurt, cottage cheese, sauerkraut and pickles.

Useful Bacteria Bacteria are also used in industrial chemical production. They produce organic chemicals and fuels. They are used in mining of minerals They are used as insecticides.

Useful Bacteria Bacteria are used to help clean up environmental disaster caused by human such as chemical and oil spills.