NOTES: 20.2 (& 20.3)

How are Bacteria Different

from Viruses?

Bacteria are different from viruses in that they:

-are much bigger

-have a different structure (made of cells) therefore are considered “LIVING”

-can reproduce (unlike viruses, which require a host cell)

Bacteria are PROKARYOTES (no nucleus)

Bacteria have 2 Kingdoms:

Kingdom Archaebacteria and Eubacteria

Some bacteria you

are probably

familiar with…

Bacteria…

are unicellular

are prokaryotes

have ribosomes

have genes (typically in a single circular

chromosome)

often have a cell wall (protection)

**many antibacterial drugs target the

cell wall

The Size of Bacteria

Prokaryotes typically range in size from

1-5 μm (micrometers)

The Structure of Bacteria

3 basic shapes: rod-shaped,

spherical, spiral

they may form long chains, large

clumps / clusters, or colonies

movement: propelled by flagella

or cilia

“Breathing” (RESPIRATION) in Bacteria

some are aerobic: respiration requires oxygen

-obligate aerobes - cannot survive without oxygen

EX: Mycobacterium tuberculosis (TB)

some are anaerobic: respiration without oxygen

-obligate anaerobes - cannot survive with oxygen

EX: Treponema pallidum (syphilis)

How Do Bacteria Obtain Energy?

some make their own food (like plants) =

AUTOTROPHS

some obtain their food (like us) =

HETEROTROPHS

These bacteria eat the

nutrients in the agar.

Reproduction in Bacteria most reproduce through

BINARY FISSION (asexual) =

offspring are clones

other bacteria exchange genetic information through CONJUGATION (a.k.a. bacteria “sex”)

-a hollow bridge forms between the 2 bacterial cells and genes move from 1 bacterium to the other

-ADVANTAGE: increases genetic diversityin the bacterial population

if food and space are not an issue, bacteria divide at

astonishing rates!

some can divide every 20 minutes!!

if this were to continue to happen, the bacteria would

reach a mass of 4000x the mass of the Earth in 48

hours!

EXPONENTIAL GROWTH!!!

How Bacteria Can Be Controlled:

STERILIZATION:

-heating / boiling OR use a disinfectant

(i.e. alcohol, bleach)

FOOD PROCESSING:

-boiling, frying, steaming, refrigeration, salt,

vinegar

As labeled by

humans, there are

both “BAD”

bacteria and

“GOOD” bacteria.

Bacteria that cause illness and

disease (PATHOGENIC)

Bacterial diseases:

-diptheria, tuberculosis, typhoid fever, tetanus, syphilis, cholera, bubonic plague

How are the diseases caused?

-bacteria damage the cells & tissues of an organism directly by breaking down the tissues for food

-OR…bacteria release toxins (poisons) that travel through the organism’s body

WARNING:

Disturbing Picture!!

Flesh-eating bacteria

Ocean warning!

Diseases caused by bacteria:

Disease Transmission Symptoms Treatment

Tuberculosis Inhale Fatigue, cough,

fever, chest pain

antibiotics

Tetanus Puncture

wound

Stiff jaw, muscle

spasms,

paralysis

Clean wound,

antibiotics,

antitoxin

Strep throat Inhale or

ingest through

mouth

Fever, sore

throat, swollen

gland

Antibiotic

Lyme disease Bite of infected

tick

Rash at site of

bite, chills,

aches

Antibiotic

Cholera Contaminated

water

Diarrhea,

vomiting,

dehydration

Antibiotics,

replace fluids

Since 1900, the life expectancy in the U.S.

has increased from 47 years to 75

years…WHY???

better public health

improved water / sewage treatment

nutrition, medical care

ANTIBIOTICS

• bacteria that humans use and need in

their everyday lives.

Escherichia coli (Esh-er-ish-e-ah coal-eye): one of many kinds of microbes that live in your gut. Wanted for helping you digest your food every day.

Saccharomyces cerevisiae (sack-arrow-my-seas sair-uh-vis-ee-ay): a.k.a. baker's yeast. Wanted for making bread rise.

Pseudomonas putida(sue-doe-moan-us poo-tea-dah): one of many microbes wanted for cleaning wastes from sewage water at water treatment plants.

Lactobacillus acidophilus (lack-toe-bah-sill-us acid-off-ill-us): one of the bacteria gang wanted for turning milk into yogurt.

Arbuscular mycorrhizas (ar-bus-que-ler my-kuh-rye-zuh): one of a soil-living fungus family. Wanted for helping crops take up nutrients from the soil.

Streptomyces(strep-toe-my-seas): soil bacteria wanted for making streptomycin, an antibiotic used to treat infections.

Bacillus thuringiensis (bah-sill-us ther-in-gee-in-sis): a.k.a "Bt", a common soil bacterium. Wanted as a natural pest-killer in gardens and on crops.

Good Bacteria in Summary:

1) Nitrogen Fixation

most organisms need

nitrogen for DNA, RNA,

proteins, and ATP

few organisms can

convert nitrogen gas into

useable nitrogen so they

need the help of bacteria that

live in the roots of legumes

(beans, peas, etc…)

Good Bacteria in Summary:

2) Recycling of Nutrients

decomposing bacteria break down dead

organisms and wastes, returning nutrients

to the environment

Good Bacteria in Summary:

3) Foods and Medicines

EX: Swiss cheese, pickles, yogurt

EX: antibiotics that destroy other

types of bacteria (streptomycin,

erythromycin, etc.)

Antibiotics

How Do You Treat a

Bacterial Infection?

if prevention fails, take ANTIBIOTICS

antibiotics kill bacteria without harming the cells of humans or animals

-they interfere with the cellular processes of bacteria (e.g. stop cell wall synthesis)

many antibiotics are produced naturally by living organisms

-ex: penicillin

others are synthetic (man-made)