Bacteria

Bacteria

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What are bacteria? Bacteria are among the

smallest living organisms. They usually band together in

colonies. Bacteria can be autotrophic,

make their own food or

heterotrophic, feed off of other organisms.

E. Coli O157:H7 can make you very sick.

This E. coli helps you digest food.

Characteristics of Bacteria

Three basic shapes Rod shaped called bacilli (buh-

sill-eye) Round shaped called cocci (cox-

eye) Spiral shaped

Bacilli

Cocci

Spiral

Structure of Bacteria

Cell wall resists osmotic pressure

Flagella movement

Pili Attachment

Capsule protection and biofilms

Bacteria have these features:


Structure of Bacteria Cell Wall made of Peptidoglycan May have a sticky coating called the Capsule for attachment

to host or other bacteria Have small rings of DNA called Plasmids Unicellular Small in size (0.5 to 2μm)


Some bacteria (often pathogens) are surrounded by a thick polysaccharide capsule. This is a loose jelly-like or mucus-like layer. It helps prevent immune system cells from reaching the bacteria, and it forms part of biofilms.

Capsule


Pili are hairs projecting from the surface. They are composed of pilin protein.

There are several types: DNA can be transferred between bacteria by

conjugation, which is initiated when sex pili on the donor cell attach to and draw in the recipient cell.

Fimbriae are pili used to attach the bacteria to target cells (in infection) or to surfaces, where they form a biofilm.


Flagella are long hairs used to propel the cells. They are composed of flagellin protein. At the base of each flagellum is a motor

embedded in the membrane and cell wall. The suffix “-trichous” is used to describe the

placement of flagella: e.g. lophotrichous = several flagella all clustered at one end

Flagella


Chemotaxis: Bacteria move toward the source of nutrients by swimming up the chemical gradient. When moving up the gradient, bacteria rarely

tumble, but when moving across it, or in the opposite direction, tumbling is frequent.

This produces a net motion in the proper direction.


Some bacteria can form very tough spores, which are metabolically inactive and can survive a long time under very harsh conditions. Allegedly, some bacterial spores that were

embedded in amber. Panspermia: the idea that life got started on

Earth due to bacterial spores that drifted in from another solar.

Spores

Spores survive very high or low temperatures.

Movement and feeding

Bacteria get around in many ways. Some bacteria move

using flagella. Others have a slimy

layer to grip surfaces. Some are carried by the

movement of air or liquids.

.

Movement and feeding Photosynthetic bacteria can

make their own food from sunlight and carbon dioxide, just like plants.

Bacteria that break down dead organisms get their food by absorbing it.

These blue green bacteria use sunlight

to make food.

The importance of bacteria

Bacteria are useful in many areas of industry. Yogurt and cheese are

made with certain types of bacteria.

Bacteria break down waste products in sewage.

Bacteria can help clean up oil spills.

The importance of bacteria

Bacteria are an important part of the nutrient cycles that all life depends upon.

The importance of bacteria Bacteria are “nature’s

recyclers.”

Harmful effects of bacteria

Certain bacteria act as pathogens and cause tetanus, typhoid fever, pneumonia, syphilis, cholera, food-borne illness and tuberculosis.

Streptococcus bacteria may cause small infections like strep throat and some serious diseases like pneumonia.

Some of the stomach bacteria enter the body through the mouth, and they can survive in the acidic conditions in the stomach.


Typhoid fever

Acidic condition


Campylobacter is a group of bacteria that can create illnesses in humans and is a common cause of food poisoning.

Harmful bacteria in food cause botulism, which can cause paralysis or even death if even one-millionth of the bacterium is ingested.

Yersinia pestis or bubonic plague, is a rod-shaped type of bacterium which is well-known for its harmful nature.


Bacteria-carrying fleas found on animals such as rats and mice transmit the bacteria that are believed to have caused the deaths of millions of people in human history.

Antibiotics are widely used to kill harmful bacteria.

Where do you get a pathogen ?

Contact with people who are sick Direct or indirect

Food, Water, or other Surfaces that are contaminated

Indirect contactDirect contactFoods that could be

contaminated

Where do you get a pathogen?

Indirect Contact

Direct Contact

Foods and water may be contaminated

How can I avoid pathogens?

Wash your hands often so you won’t transfer bacteria to your mouth or food

Warm water with soap for 20 seconds, rub hard between fingers and nails

• Cook food thoroughly to kill any pathogens that may be in your food

• Store food properly to limit pathogen growth– Cold temperatures (40F)

The End

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Bacteria