BACTERIA

1. BACTERIA

2. Bacteria are Prokaryotes • Prokaryotes were the initial inhabitants of Earth and today are found almost everywhere • Have no nuclear membrane nor membrane-enclosed organelles • Inside the cell is one large circular strand of DNA or RNA

3. Bacteria In General: • Are the oldest and most abundant living organisms on Earth • All share basic structures but are diverse in cell shape and nutritional patterns • Affect humans in various ways: cause disease, spoil foods, can be resistant to antibiotics • Fix nitrogen for plants, decompose organic matter, manage hazardous waste, aid animal digestion, help create dairy products

4. General Structure of Bacteria:

5. Further Investigation... http://www.cellsalive.com/cells/bactcell.htm

6. Archaebacteria: • Oldest of all life forms • Hypothesized that all life kingdoms descended from ancestors of this group! • Organisms in this taxon possess: -cell walls -single chromosome -unicellular in nature Over half the genes in archaebacteria differ from those of eubacteria

7. 3 Main Orders of Archaebacteria: METHANOGENS -live in oxygen free places, such as animal intestines

8. 3 Main Orders of Archaebacteria: HALOPHILES -salt loving -found in the Dead Sea

9. 3 Main Orders of Archaebacteria: EXTREME THERMOPHILES -live in hot, acidic environments such as hot springs

10. Eubacteria • Most successful of prokaryotes • Organisms belonging to this taxon possess: -cell walls -single chromosome -unicellular in nature

11. Basic Bacteria Structure: • Both archaebacteria and eubacteria are classified according to: • Cell Shape • Gram Stain • Nutrition • Respiration

12. 1. Cell Shape Bacteria cell shapes come in 3 basic forms: • Round – coccus • Rod – bacillus • Spiral - spirillum

13. 1. Cell Shape • Cocci that live as separate cells = monococci. • Cocci live in pairs = diplococci • Cocci live in linear chains = streptochocci. • Cocci live in grapelike clusters = staphylococci • Bacilli also exists as single, pairs or chains or random attachments • Spiral bacteria exist only as single cells

14. 2. Gram Stain • Gram staining is a differential staining procedure that allows the categorization of bacteria into 2 groups based on their ability to retain a violet stain colour • 2 groups: Gram Positive OR Gram Negative (purple colour) (pink colour)

15. Differences in Gram Staining • Gram-positive organisms are able to retain the crystal violet stain because of the high amount of peptidoglycan in the cell wall. • Gram-positive cell walls typically lack the outer membrane found in Gram-negative bacteria.

16. 3. Nutrition • All cells need energy and a source of carbon for cellular respiration. major energy source light= photosynthetic bacteria Inorganic compounds = chemosynthetic bacteria Photoautotrophsphotoheterotrophschemoautotrophschemoheterotrophs

17. 3. Nutrition Photoautotrophs: -can synthesize their own organic compounds from sunlight -Cyanobacteria (a.k.a. Blue green algae) -forms blooms in polluted water due to nitrate and phosphate run-off into the water -use up oxygen in lakes/ponds/water source

18. Bloom of Blue-Green Algae:

19. 3. Nutrition Chemoautotrophs: -obtain energy by breaking apart chemical bonds in inorganic compounds such as hydrogen sulphide and ammonia Chemoheterotrophs: -live everywhere -some are parasites and live off hosts -some are saprobes and consume decomposing hosts

20. 4. Respiration • All living things must carry out cellular respiration to receive energy for life’s functions • Bacteria differ in whether or not they need oxygen • Bacterial respiration falls into 2 basic categories: • Aerobes -cellular respiration involves oxygen to produce energy from food that is broken down -obligate aerobes absolutely need oxygen for survival

21. 4. Respiration • Anaerobes -bacteria that carry out cellular respiration in an oxygen-free environment -if the presence of oxygen kills these organisms, they are called obligate anaerobes

22. 4. Respiration Example: obligate anaerobe = soil bacterium called Clostridium botulinumthat produces toxins that can cause an extreme form of food poisoning called botulism 3. Facultative Anaerobes: can survive in either environment

23. Bacterial Reproduction Depending on environmental conditions, bacteria can reproduce in a variety of manners: • Under favourable conditions • Under unfavourable conditions • Under extreme conditions

24. Under Favourable Conditions: • All bacteria use binary fission (asexual reproduction) under ideal conditions • Produce EXACT copies of themselves: parent cell divides into 2 identical offspring • Can divide every 15-20 minutes • In 12 hours there is 10 to 100 million bacteria! • Genetic mutations occur which increase their diversity and ability to survive • Due to fast reproduction rate bacteria mutate often – 2000/day • If the mutation is favourable then it spreads through the population quickly

25. Binary Fission

26. Under Unfavourable Conditions • Will reproduce using conjugation if conditions begin to fail (lack of food, heat, dessication –drying out- or space) • 2 bacteria cells connect to each other by long protein bridges called a pilus between them • 1 cell transfers a copy of their plasmid (smaller ring of DNA with fewer genes than chromosomes) to the other cell • The bacteria that received this plasmid now has a different genetic make up and this thereby increases their chances of survival • Example: bacteria become resistant to antibiotics

27. Conjugation

28. Under Extreme Conditions: • Bacteria form structures called spores – one such is called an endospore • Many gram positive bacteria form these spores • Endospore: bacteria produces a thick wall around DNA and cytoplasm • This enables them to remain dormant for long periods (months) until conditions are once again favourable • So, endospores do not metabolize or reproduce but simply exist until conditions become favourable

29. Endospores

30. Endospores • Example of Clostridium bacteria with characteristic drumstick-shaped endospore-producing cells. • The dark rod-shaped cells are vegetative cells. • The clear ovals are endospores, and the objects consisting of both dark rod and clear oval are vegetative cells producing endospores.