1. Chapter 19: Bacteria

2. How Human are you?
There are more microbial cells in our bodies than there are human cells!
Of the 100 trillion cells that make-up the human body 90 trillion are bacterial
Humans are ~90% Bacterial
Everyone has about 1 kg in weight of bacteria in their gut.
Each gram of feces contains 100,000,000,000 (100 billion) microbes.
Human adults excrete their own weight in fecal bacteria every year.

3. Classifying Prokaryotes
DOMAIN BACTERIA – Kingdom Eubacteria
Single-celled prokaryote
Have peptidoglycan (protein carbohydrate) cell walls
Can form colonies of clumps or filaments.
Three basic shapes: Cocci (round), bacilli (rod) & spirilla (spiral)
Strepto – occurs in chains.
Staphylo – occurs in clusters..

4. Basic Structure Cell wall – protects the cell & gives it shape.
Outer membrane – protects the cell against some anibiotics (only present in gram-negative)
Cell membrane – regulates movement of materials into & out of the cell; contains enzymes important to cellular respiration.
Plasmid – circular piece of DNA that contains some genes obtained through genetic recombination.
Capsule & Slime layer – protect the cell & assist in attaching the cell to other surfaces.
Basic Structure
Ribosome
Cell Membrane
Cell Wall
Pilli
DNA (circular)
Peptidoglycan
Flagella

5. Classifying Prokaryotes
DOMAIN ARCHAEA – Kingdom Archaebacteria
Genes that resemble eukaryotic genes & some that resemble prokaryotes.
Have unusual lipids in their cell membranes
Found in EXTREME environments!
Cell walls lack peptidoglycan
Have introns in their DNA
Single-celled prokaryote

6. Archaebacteria Methanogens Convert H2 & CO2 into methane CH4
Anaerobic bacteria
Found in bottoms of swamps, sewage & intestinal tracts of animals.
Extreme Halophiles
Salt loving
Found in Great Salt Lake & Dead Sea
Thermoacidophiles
Live in extreme acidic & hot environment

7. Prokaryote Evolution
Fossil Evidence indicates bacteria existed about 3.5 billion years ago.
Eukaryotes existed about 2.5 billion years ago.
Bacteria evolved to adapt to almost any environment, from ocean trenches to thermal vents.

8. Identifying Prokaryotes
Prokaryotes are identified by characteristics such as:
the way they obtain energy
shape
type of cell wall
the way they move

9. V. Ways Bacteria are Identified
I. Shapes of Bacteria:
a. Bacilli - rod-shaped

10. b. Cocci - round shaped
Staphylococcus - cocci in
clusters
Streptococcus - cocci in chains
Diplococcus - cocci in pairs

11. Spirilla - spiral shaped Ex: Treptonema pallidum

12. Metabolic Diversity
Chemoheterotrophs – organisms that must take in organic molecules for both energy and a supply of carbon.
Photoheterotrophs – organisms that are photosynthetic, but still need to take in organic compounds as a carbon source.
Chemoautotrophs – make organic carbon molecules from carbon dioxide and other inorganic compounds using energy from chemical reactions.
Photoautotrophs – use energy from sunlight to convert carbon dioxide and water to carbon compounds.

13. Releasing Energy
Obligate aerobes – organisms that require a constant supply of oxygen in order to live. EX: Mycobacterium tuberculosis, the bacterium that causes tuberculosis.
Obligate anaerobes – do not require oxygen; some may be killed by O2! EX: Clostridium botulinum, found in soil and can grown in canned food causing fatal food poisoning.
Facultative anaerobes – can survive with or without O2. EX: E. coli, can live in the large intestines and contaminated water.

14. Growth & Reproduction
Binary Fission – bacterium doubles in size, it replicates its DNA and divides in half.

15. Growth & Reproduction
Conjugation – the process by which two living bacteria bind together and one bacterium transfers genetic information to the other.
Sex pili

16. Growth & Reproduction
Endospore – protects the cell against harsh environmental conditions, such as heat and drought. May allow the bacterium to survive for thousands of years.

17. Importance of Bacteria
Decomposers – break down the nutrients in dead matter & atmosphere.
Nitrogen – Fixing Bacteria (Nitrogen fixation)
Live freely & symbiotically with plants
Rhizobium; converts N2 into a form of nitrogen plants can use.
Found in legumes (bean type plants)

18. Importance of Bacteria
Phylum Cyanobacteria
Photosynthetic
Encased in jelly-like substance & cling together
Contain enzymes for fixing atmospheric nitrogen & make it available to plants.
Some thrive on phosphates & nitrates in lakes & ponds.

19. Importance of Bacteria
Phylum Cyanobacteria
Eutrophication or Population Bloom – the sudden increase in the number of cyanobacteria due to a high availability of nutrients.
When cyanobacteria die, they are decomposed by heterotrophic bacteria. This increase in heterotrophic bacteria depletes O2 in the water, harming other organisms that live there.

20. Human Uses of Bacteria Food – baking & beverages
Clean up oil spills, rivers & streams
Make pharmaceuticals
Aid in digestion

21. Bacteria & Disease
Pathogen – bacteria that cause disease or a disease causing agent.
Exotoxins – toxic proteins secreted by bacterial cells, includes some of the most potent poisons known.
Clostridium botulinum – one gram of the exotoxin that causes botulism could kill 1,000,000 people!
Staphylococcus aureus – harmless, found on skin; if it enters the body through a wound it can cause layers of skin to slough off, vomiting, severe diarrhea & deadly toxic shock syndrome.

22. Bacteria & Disease
Endotoxins – are NOT secretions; but components of cell walls in bacteria: glycolipids, which are large molecular complexes of polysaccharides & lipids.
All endotoxins induce the same general symptoms: fever, aches and sometimes a dangerous drop in blood pressure (shock).
Salmonella – produces endotoxins that cause food poisoning & typhoid fever.

23. Bacteria & Disease Lyme Disease
Most widespread pest carried disease in U.S.
Caused by Borrelia burgdorferi, a bacterium carried by ticks that live on deer & field mice.
Antibiotics can cure the disease if administered within a month of exposure.
If untreated, it can lead to arthritis, heart disease & nervous disorders.

24. Bacteria & Disease
Yersinia pestis – the bacterium that causes bubonic plague throughout Europe. Carried by fleas.
It also played a role in battle, when armies hurled the bodies of plague victims into enemy ranks.

25. Bacteria & Disease Bacillus anthracis
Found naturally in soil where grazing animals such as sheep, cattle & goats are located.
Easy to obtain, grow & it forms hardy endospores that can survive for years.
Upon entering the bloodstream, anthrax will actively metabolize & multiply.
Anthrax will release 3 proteins that combine to form a toxin that destroys body tissues & cells of the immune system.
Modes of entry: cutaneous, inhalation, ingestion

26. Bacteria & Disease
Bacillus anthracis

27. Bacteria & Disease

28. Antibiotics
Antibiotics are drugs that combat bacteria by interfering with various cellular functions
Some bacteria are antibiotic-resistant and destroy antibiotics, or prevent entry of the antibiotic into the cytoplasm.

29. Antibiotics
Bacteria can be tested for their sensitivity to antibiotics by growing them in a petri dish with paper disks containing different antibiotics.
As the antibiotics diffuse into the agar, the bacteria’s growth will be inherited by the antibiotics if the bacteria are sensitive to that antibiotic.