Bacteria

Learning Targets: Describe the structure and function of a typical bacterial cell Classify bacteria based on shape and arrangement Describe how bacteria reproduce Summarize the history and adaptations of bacteria Evaluate the importance of bacteria Identify diseases cause by bacteria

What are bacteria? Prokaryotes classified in 2 kingdoms unicellular lack a nucleus and membrane-bound organelles classified in 2 kingdoms archaebacteria eubacteria

What are archaebacteria? live in extreme habitats Methanogens = oxygen-free environments Halophiles = very salty environments Thermoacidophiles = hot, acidic environments

What are eubacteria? Heterotrophs Found everywhere parasites obtain nutrients from living organisms saprophytes feed on dead organisms/organic waste

Autotrophic eubacteria photosynthetic autotrophs Obtain energy from light Make own food Cyanobacteria

Chemosynthetic autotrophs break down & release the energy of inorganic compounds containing S & N to make organic molecules that are their food

Anatomy of a bacterium? Cell wall gives shape & prevents osmosis from bursting the cell Capsule surrounds cell wall Circular chromosome (single DNA molecule) not enclosed in a nucleus contains most of the genes Few genes are located in a small circular plasmid Plasma (cell) membrane regulates what enters & leaves the cell Hair-like pilus helps a bacterium stick to a surface helps exchange DNA Whip-like flagellum enable them to move

Flagellum Clip 1 Clip 2

Bacterial culture techniques                             Carefully & thoroughly swab selected surface Transfer bacteria from broth culture to nutrient agar plate by touching swab to agar surface in a single spot Isolate bacterial colonies by streaking the plate, being careful not to tear agar Incubate plate

Pure culture population of bacterial cells growing in the absence of other types streak plate technique is used to spread millions of cells so that some are deposited a distance from all others these cells grow & reproduce, forming an isolated colony (represents a pure culture)

How can bacteria be identified? Gram staining checks for differences in the structure of their cell walls gram-positive bacterial cells turn purple gram-negative cells turn pink doctors know which antibiotics to use based on the results

Penicillin inhibits Stapylococcus Antibiotics Bacteria live in hypotonic environments higher concentration of water outside than inside cell water is always trying to enter cell A bacterial cell remains intact & doesn’t burst open as long as its cell wall is intact scientists used this need to develop antibiotics Penicillin inhibits Stapylococcus

Disc diffusion antibiotic discs release antibiotic into surrounding medium zone of growth inhibition Area of no bacterial growth around the disc will occur if the bacteria are susceptible to the antibiotic

Antibiotic resistant bacteria

Shapes of bacteria another way to identify bacteria sphere = coccus rod = bacillus spiral = spirillium

Growth pattern of bacteria also used to identify bacteria pairs = diplo- grape clusters = staphylo- long chains = strepto-

Draw the following… Diplococcus meningitidis causes meningitis Streptococcus pneumoniae causes pneumonia Staphylococcus aureus causes toxic shock syndrome and boils

2 kinds of Reproduction

How do bacteria asexually reproduce? Binary fission makes a copy of its chromosome cell grows larger chromosomes move to opposite ends of the cell a wall begins to form in the middle 2 new cells are genetically identical

Binary fission video clip

How do bacteria sexually reproduce? Conjugation pilus = bridge-like structure that one bacterium uses to connect to another 1st bacterium transfers all or part of its chromosome to the second through the pilus 2nd bacterium has a mix of genetic material & reproduces by binary fission produces bacteria with a whole new genetic combination

Conjugation video clip

Diversity of metabolism Obligate aerobes require oxygen for respiration Mycobacterium tuberculosis causes tuberculosis Obligate anaerobes are killed by oxygen Treponema pallidum causes syphilis Clostridium botulinum causes botulism Mycobacterium tuberculosis Clostridium botulinum

Facultative anaerobes Bacteria that prefer an aerobic condition Can make ATP with no oxygen if put into that situation Ex’s Staphylococcus (g+) E. coli (g-) Listeria (rare food borne illness-25% lethal) Corynebacteria- skin flora

Which tube flourishes in O2?

Whats up?

A survival mechanism Endospore tiny structure that contains bacterium’s DNA & small amount of cytoplasm encased by tough outer covering that resists drying out, temperature extremes, & harsh chemicals bacterium rests & doesn’t reproduce

The importance of bacteria Disease-causing bacteria are few in number compared with the number of harmless & beneficial bacteria on Earth help to fertilize fields help to recycle nutrients help to produce foods & medicine

Food Safety

Nitrogen fixation All organisms need nitrogen, yet few can directly use it from air nitrogen fixation – process of converting nitrogen gas into ammonia other bacteria convert ammonia into nitrate & nitrite which plants can use Animation Rhizobium on plant nodules convert nitrogen gas into ammonia

Recycling of nutrients Life could not exist if decomposing bacteria didn’t break down organic materials in dead organisms and wastes returns nutrients to the environment

Food and medicines During respiration, different bacteria produce diverse products which have distinctive flavors & aromas vinegar yogurt & cheeses sauerkraut sour cream Some bacteria produce important antibiotics that destroy other types of bacteria streptomycin erythromycin bacitracin neomycin

What diseases do bacteria cause? Diseases Caused by Bacteria Disease Transmission Symptoms Treatment Strep throat inhale/ingest fever, sore throat, swollen glands antibiotic Tuberculosis inhale fatigue, fever, night sweat, cough, chest pain Tetanus puncture wound stiff jaw, muscle spasms, paralysis antibiotic, antitoxin Lyme disease tick bite rash, chills, body aches, joint swelling Cavities bacteria toothache fillings Diphtheria inhale/contact sore throat, fever, heart/breathing failure vaccine, antibiotics

Bacteria and Disease 50% of all diseases are thought to be caused from bacteria In 1900, tuberculosis and pneumonia were the two most common diseases Factors that increased life expectancy: Less poverty, better health systems, increased water and sewage systems, increased nutrition, better medical care

Are there bacteria on cell phones?

Controlling Bacteria Cooking Foods Referigeration/freezing Drying foods Pickling