BacteriaOur invisible friends

Bacteria are prokaryotes

Pro – before

Karyon – nucleus

The simplest forms of life are prokaryotes.

Earth’s first cells were prokaryotes.

Lots of Them!

Prokaryotes are Earth’s most

abundant life forms.

They can survive in many

environments.

They can get energy from many

different sources.

Kingdoms

Bacteria fall

into two

kingdoms:

Archaebacteria

(Archaea)

Eubacteria

Archaebacteria

Archae = early or primitive

In fact archaebacteria have a more advanced structure than eubacteria and share characteristics with eukaryotes

Cell wall lacks peptidoglycan

Genes and enzymes behave more like Eukaryotes

Cells have three RNA polymerases like eukaryotes

Archaebacteria

Many Archaebacteria are often referred to as

extremophiles. They have the unique ability

to survive in environments where other

organisms cannot survive.

These extreme environments are anaerobic

(lacking oxygen) and are believed to

resemble conditions that existed when life

first evolved on earth, billions of years ago.

Archaebacteria

Three major groups of archaebacteria

include:

Methanogens – methane-producing organisms

Extreme Thermophiles – thrive in temperatures

up to 110°C

Extreme Halophiles – thrive in very salty

environments

Eubacteria

True bacteria

More primitive than archaebacteria

Cell wall made of peptidoglycan

Cells have only one RNA polymerase

Similarities

Common characteristics of Archaebacteria

and Eubacteria:

1. Cells are prokaryotic, all are single celled

2. Cells contain no membrane-bound organelles

3. Cells reproduce asexually by binary fission or

sexually by conjugation

Eubacteria Classified by Shape

Cocci (ball-shaped)

Streptococcus mutans

Bacillus (rod-shaped)

Clostridium botulinum

Spirilli (spiral-shaped)

Treponema palladium

Eubacteria Classified by Shape

Reproduction & Growth

Asexual Reproduction – only one parent is

involved

Binary Fission – simpler than mitosis. Single stand of bacterial DNA replicates

This identical genetic material is transferred to each new cell

Bacterium produces a cross wall and divides into two identical

cells

Binary Fission

Reproduction & Growth

Sexual Reproduction – two parents involved

Not common in bacteria

Conjugation Transfer of genetic material between bacterial cells by

direct cell-to-cell contact or by a bridge-like

connection between two cells

The recipient cell now has an altered set of

characteristics, due to recombination of the DNA

Conjugation

Factors Influencing Bacterial Growth

Physical Factors: Temperature

Oxygen

pH

Osmosis

Nutritional

Requirements: Energy source

Carbon

Nitrogen

Water

Other Minerals

Organisms having complex nutritional requirements and

needing many growth factors are said to be fastidious

Harmful Effects of Bacteria

Bacteria are best known for being:

pathogenic - disease causing. The anthrax causing bacteria Bacillus anthracis was

the first bacterium proven to cause disease.

Virulence Factors

Virulence factors are molecules expressed

and secreted by bacteria that enable them to

achieve the following: Immunoevasion, evasion of the host's immune

response

Immunosuppression, inhibition of the host’s immune

response

Entry into and exit out of cells

Obtain nutrients from the host

Symptoms

Bacteria cause disease in three major ways:

1. Their sheer numbers burden the host’s tissues

and interfere with normal function

2. The bacteria cells destroy the hosts cells and

tissues

3. Some bacteria produce poison called toxins

which shut down the hosts tissues

Spread and Protection

Infectious bacterial diseases are spread from

one individual to another in a variety of

ways: Moisture droplets in the air

Dust

Direct contact

Fecal contamination

Animal bites

wounds

Spread and Protection

Most people have built in protection

provided by the body’s own defense

mechanisms: Immune System

Other methods of protection include: Sterilization/disinfection

Use of antiseptics

Extermination of animals that carry bacterial disease

Immunizations and administration of antibiotics

Examples of Pathogenic Bacteria

Type of Bacteria Disease/destruction produced

cloasridia botulism, tetanus, and gangrene

streptococci strep throat, scarlet fever, and pneumonia

staphylococci boils, food poisoning, and skin infections

lactobacilli souring of milk

pseudomonads gasoline spoilage

bacilli destruction of silkworms

staphylococci and pseudomonads food spoilage

coliform bacteria Pollution of water sources, soft rot in plants,

gastroenteritis and dysentery in humans

spirilla cholera and syphilis

Bacteria: Friend or Foe?

The usefulness of bacteria far outweigh the

damage they cause.

One of the most important jobs of bacteria

are the recycling they do as decomposers. Bacteria are the primary organism responsible for

converting dead plants and animals into natures raw

materials. These nutrients are essential for living

plants and animals.

Beneficial Effects of Bacteria

Type of Bacteria Beneficial Effects

clostridia production of butanol and acetone from molasses

acetobacter production of vinegar from alcohol

intestinal bacteria food digestion; synthesizing of vitamins in humans

eg. To regulate blood clotting

lactobacilli production of lactic acid form sugar

aztobacter, nitrobacter fixation of nitrogen in soils

streptococci, lactobacilli production of dairy products

eg. Cheese, buttermilk, and yogurt

streptomyces source of antibiotics

eg. Streptomycin, terramycin, neomycin, and

erythomycin

Bacteria Cleaning Crew

Some bacteria literally 'live

on oil,' just as some people

live on meat and potatoes.

And they consume it with

just as much relish.

Such bioremediation cannot

only help to clean up oil

spills, but also chlorinated

chemicals and leaks from

storage tanks.

Probiotics

Probiotics - live microorganisms that are

healthy for the host organism

Lactic acid bacteria (LAB) and bifidobacteria are

the most common types of microbes used as

probiotics

Probiotics are commonly consumed as part

of fermented foods including:Yogurt Dietary Supplements

Buttermilk

Antibacterial Resistance

Over the past 50 years, many disease-causing

bacteria have slowly developed resistance to

antibiotics

This resistance arises due to variations within

a bacterial population allowing for natural

selection

Antibacterial Resistance

Bacteria resistant to antibiotics contain

R (resistance) Factors These R factors are plasmids with special genes that

code for enzymes which inactivate specific drugs

The R factors are transferred and recombined in

conjugation

“The misuse of antibiotics could cause

serious problems for society”