Bacteria19-1

https://www.youtube.com/watch?v=qCn92mbWxd4

(bacteria introduction)

Two Kingdoms

• Bacteria are divided into two separate kingdoms.– Archaebacteria

• Able to live in very extreme environments.• Lack peptidoglycan in their cell walls• Different membrane lipids• DNA sequences are more like eukaryotes than eubacteria

– Eubacteria• Represents all other bacterial cell and makes up most of the

prokaryotic cells on the planet.• Contains peptodoglycan in their cell walls

Classification of Archaebacteria

• Classified based upon the environment in which they are able to live.– Thermophiles

• Able to tolerate very high temperatures (60-100)– Able to live in hot springs or deep sea vents

– Halophiles • Able to tolerate very salty conditions.

– Great Salt Lake, Dead Sea

– Methanogens • Live in anaerobic environments, such as swamps.• Produce methane as a result of their metabolic processes.

Classification of Eubacteria

• Classification based upon their means of nutrient obtainment(…..how they eat.)– Photoautotrophs– Chemoautotrophs– Heterotrophs– Photoheterotrophs

Basic Characteristics

• “Ubiquitous”- they are everywhere• Prokaryotic

– Single celled; lacking a nucleus

• Genetic Material Circular – chromosome attached to a cell wall– Plasmids

• Circular piece of DNA that replicates during conjugation.

• Cell Wall• Reproduction occurs via binary fission

– Little to no genetic variation unless conjugation takes place

• Great metabolic diversity – https://www.youtube.com/watch?v=vAR47-g6tlA (archaea,

bacteria, and protist background – 12 min)

Two Types of Cell Wall Structures

• Gram positive -- Has one cell wall outside of plasma membrane and stains purple in a Gram stain.

• Gram Negative— has an additional membrane layer beyond the peptidoglycan and stains pink in a Gram stain.

Gram Positive Stain Gram Negative Stain

Shapes of Bacterial Cells

• Bacteria can be divided up into three main shapes.– Bacillus (rod shaped)– Coccus (sphere shaped)– Spirillum (spiral shaped)

Bacillus

Coccus

Spirillum

Movement of Bacteria

• https://www.youtube.com/watch?v=6p9e0oolbmE (shapes and movement – 3 min)

Bacterial Prefixes

• Prefixes can also be attached to the beginning of a shape to add further description– Diplo- = pairs– Strepto- = chains– Stapylo- = groups\ clusters

Diplococcus Streptococcus

Stapylococcus

Bacterial Reproduction

• Bacteria usually reproduce via binary fission.– Everything inside is copied

and the cell spits in two.

• Bacteria can also undergo conjugation where genetic information is exchanged between two organisms.

Releasing Energy

• Bacteria can undergo cellular respiration and fermentation

• Bacteria can be– Obligate aerobes– Obligate anaerobes– Facultative anaerobes

Endospores

• When conditions become unfavorable, many bacteria form an endospore to survive harsh conditions that might otherwise kill them.

Notes on 19-2

• Bacteria are vital to maintaining the living world.

• Some are producers that capture energy by photosynthesis

• Others help break down the nutrients in dead matter and the atmosphere allowing other organisms to use the nutrients

Decomposers

• Why are decomposers essential to all living things?

• Can recycle dead organisms as well as human waste, organic garbage, chemical waste.

• This process purifies the water and releases nitrogen and carbon dioxide gases, and leftover products that can be used as fertilizers.

Nitrogen Fixers

• Plants and animals depend on bacteria for nitrogen.

• Plants need nitrogen to make amino acids, which are the building blocks of proteins that both plants and animals need.

• Nitrogen must be converted from atmospheric nitrogen into a form plants can use.

• Most plants have a symbiotic relationship with nitrogen-fixing bacteria (Rhizobium)

Bacteria and Disease

• Bacteria cause disease in one of two general ways.– 1. damage the tissues of the infected

organism directly breaking them down for food. (ex. tuberculosis)

– Release toxins (poisons) that harm the body. (ex. Streptococcus and food poisoning)

• Many bacterial diseases can be prevented by stimulating the body’s immune system with vaccines.

• If a bacterial infection does occur, a number of drugs and natural compounds can be used to attack and destroy the invading bacteria. (antibiotics)

• See figure 19-10

• https://www.youtube.com/watch?v=ICWLF9lccNk (bacteria animation – 2 min)

Human Uses of Bacteria

• Bacteria are used in the production of a variety of foods (cheese, yogurt, buttermilk, sour cream, cheese, pickles, sauerkraut, and vinegar)

• Industry – oil spill clean up, mine minerals, synthesize drugs and chemicals)

Controlling Bacteria

• Most bacteria are harmless, and many are beneficial (ex. normal flora)

• However, to control bacteria:– Sterilization, heating, boiling, disinfectants, frying,

steaming– Refrigeration – slows food from spoiling– Canning – preserving food for a long time.– Inhibiting growth of bacteria – salt, vinegar, sugar.– https://www.youtube.com/watch?v=TVfmUfr8VPA

(ted talk on bacteria – 18 minutes)