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– 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 foodCyanobacteria

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

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 antibioticsPenicillin 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

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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 O22?

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 bacteriacause?

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

antibiotic

Tetanus puncture wound

stiff jaw, muscle spasms, paralysis

antibiotic, antitoxin

Lyme disease

tick bite rash, chills, body aches, joint swelling

antibiotic

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