Bacteria and VirusesCh. 19

Eubacteria◦ Largest kingdom of living things◦ Live everywhere◦ Cell wall contains peptidoglycan

Archaebacteria◦ Cell wall lacks peptidoglycan◦ DNA sequences more similar to eukaryotes◦ Live in extreme environments

Classifying Prokaryotes

Shapes◦ Rod (bacilli)◦ Spiral (spirilla)◦ Spherical (cocci)

Identification

Cell walls◦ Gram-positive stained have peptidoglycan call

walls (violet)◦ Gram-negative lack peptidoglycan (red)

Movement◦ Variety of ways….

Identification

Heterotrophs◦ Chemoheterotrophs and photoheterotrophs

majority Autotrophs

◦ Photoautotrophs Cyanobacteria

◦ Chemoautotrophs

Metabolic Diversity

Obligate aerobes◦ Require oxygen all the time; aerobic respiration

Mycobacterium tuberculosis Obligate anaerobes

◦ Killed by oxygen; anaerobic respiration Clostridium botulinum

Facultative anaerobes◦ Can survive with or without oxygen; both types of

respiration Eschericia coli

Respiration

Binary fission◦ Mitotic; asexual

Conjugation◦ Gene swapping; sexual

Sporulation◦ When conditions become unfavorable DNA and a

little cytoplasm is enclosed in an endospore

Growth and Reproduction

Growth and Reproduction

Decomposers Nitrogen fixers Food industry Mining Cleaning oil spills Pharmaceuticals Oxy Clean

Bacterial Importance

Bits of DNA or RNA surrounded by a protein coat. That’s it.◦ They come in a variety of shapes and sizes◦ They must infect a host cell to reproduce.

◦ Bacteriophages are viruses that infect bacteria.

What is a Virus?

Viruses enter a host cell and use the cell’s machinery to reproduce.

◦ In lytic infections the virus reproduces immediately until the cell bursts.

◦ In lysogenic infections the viral DNA is incorporated into the host’s DNA as prophage and may remain dormant for a period of time until reproduction begins.

Viral Infection

Contain RNA instead of DNA◦ After infecting a cell the RNA is copied in reverse

to make DNA which is then incorporated into the host cell’s genome as prophage.

◦ RNA viruses mutate frequently. Rhino virus (colds) HIV

Retroviruses

Are viruses alive?

Bacteria and viruses can act a pathogens – disease causing agents (pathos = disease; gen = generating).

◦ Louis Pasteur helped formulate the germ theory of disease.

◦ Bacteria cause disease by either using cells for food or by releasing toxins (poisons) that are harmful.

Bacterial Diseases

Bacterial Diseases

Sterilization with heat Disinfectants Cold storage Vacuum packing Nitrogen/inert gases

Controlling Bacteria

Some target the cell wall of bacteria and others disrupt protein synthesis. ◦ Antibiotics are specific to the type of bacteria

they act upon.

Antibiotics

Can’t be treated with antibiotics! They don’t have a cell wall or make proteins…

◦ Best treatment is prevention; once infected it has to run its course. Symptoms may be treated.

Viral Diseases

Viral Diseases

Vaccines provide some protection and immunity to bacterial and viral diseases.◦ More to follow…

Prevention