Bacteria are classified by the Gram stain Gram

Bacteria are classified by the Gram stain. • Gram positive bacteria appear purple after Gram staining. • Gram negative bacteria appear pink after Gram staining.

Gram Positive • Gram positive bacteria have a thick cell wall rich in peptidoglycan • Gram-positive bacteria are important in industry and medicine • Many antibiotics will kill Grampositive bacteria • Examples include Staphylococcus aureus, Mycobacterium tuberculosis, Bacillus anthracis, Bacillus subtilis

Gram Negative • Gram negative bacteria have complex cell walls with less peptidoglycan • Many species of Gram negative bacteria are pathogenic (not all) • Gram-negative bacteria are often tougher to kill, resisting common antibiotics • Examples include Escherichia coli, Salmonella enteritidis, Haemophilus influenzae

Bacteria and their energy • Autotrophs • Chemotrophs • Heterotrophs

Autotrophs • Make their own energy • Using Solar energy • Eg. Cyanobacteria

Chemotrophs • Make own Energy • Using Chemical energy • Eg. Archaebacteria

Heterotrophs • Obtain food • By eating • Eg. E-coli

Bacteria Respiration • Obligate Anaerobes • Facultative Anaerobes • Obligate Aerobes • Live without Oxygen • Can live with or without oxygen • Cannot live without oxygen.

Symbiosis • Close relationship between to species in which at least one species benefits from the other • Live together for LIFE

Parasitism • Bacteria exploit the host cell, injuring them • Eg. Mychobacterium tuberculosis

Mutualism • Symbiosis in which two of the species live together in such a way that both benefit from the relationship • Eg. E-coli

Nitrogen Fixations • Process by which nitrogen in the atmosphere is converted into a form that can be used by living things.

Protection There a few big ways to protect yourself against pathogens (disease causing agents) q Antibiotics (drugs to kill bacteria) q Antivirals (drugs to treat viruses) q Vaccination (using your body’s own immune system to preemptively guard against attack)

Antibiotics Ø Antibiotics can only be used to treat bacterial infections! Ø Target specific structures on bacteria to kill them. Ø First made from a fungus (penicillin), now most are made artificially. Ø Unfortunately, antibiotic resistance (where the antibiotic doesn’t kill the target bacteria anymore) is becoming a major problem.

Antivirals Ø Antivirals can only be used to treat certain viral infections! Ø Does not “kill” or disarm the virus permanently; only shortens symptoms by 1 -2 days. Ø Usually only prescribed to patients with life threatening symptoms. Ø Just like antibiotics, there is evidence of antiviral resistance too!

Vaccination Ø Vaccines can only be used to prevent infections (both viral and bacterial) from leading to disease. Ø “Trick” your immune system to make antibodies that destroy foreign “bodies” or particles (such as bacteria and viruses). Your body remembers how to make these antibodies when the real thing invades. Ø Made from a weakened virus, inactivated virus, or by using only part of the virus/bacteria itself

VIRUS Viruses consist of DNA or RNA enclosed in a simple protein shell known as a capsid. General properties of viruses They are very small in size, from 20 -300 m. They contain one kind of nucleic acid (RNA or DNA) as their genome. They are metabolically inert They are obligate intracellular parasites. They are only seen by electron microscope. They are unaffected by antibiotics. They are sensitive to interferon. Morphology of viruses

Morphology of viruses