Bacteria

1. Bacteria Chapter 23

2. Bacteria • Microscopic prokaryotes • Most numerous organisms on Earth • Most ancient; earliest forms of life • Bacteria are part of every environment on Earth • Many are adapted to places where nothing else can live

3. Bacterial Evolution • Rock deposits in Australia contain fossils of bacteria 3.5 byo; in relation: • 1st Eukaryotic cells (protists) 2.5 bya • Modern Humans only came about 100,000 years ago • So, all modern organisms evolved from bacteria

4. Bacterial Classification • PROKARYOTIC: single-celled; no nucleus or membrane-bound organelles • Few morphological differences between types of bacteria • Do not vary much in shape & size like other organisms • Grouped into taxa based on structure, physiology, molecular composition, & reaction to specific types of stains

5. Classification Bacteria used to be grouped into a single Kingdom, called Monera Today, we separate them into 2 kingdoms, based on difference in ribosomal RNA • Eubacteria • Common “germs” • Simply called “bacteria” • Archaebacteria • Ancient, extremophiles

6. Archaebacteria • Have a unique form of rRNA • Cells walls characterized by absence of peptidoglycan • Peptidoglycan: protein-carb compound found in cell walls of eubacteria • Thought to be the ancestral organisms that gave rise to other (more modern) forms of life

7. Archaebacteria • Found in extreme environments • More common than once thought, example: • Methanogens:broad phylogenetic group of archaebacteria • Convert H2 & CO2 into food and methane CH4 gas • Found anaerobic areas; oxygen is poison to many of these • Intestinal tracts of humans & cows

8. Archaebacteria • Extreme Halophiles: salt-loving archaebacteria; live in high salt concentration environments • Great Salt Lake & Dead Sea

9. Archaebacteria Thermoacidophiles: • live in extreme acidic environments, high temp., low pH • Deep sea hydrothermal vents • Hot springs, geysers

10. Eubacteria • Divided into MANY different phyla according to evolutionary relationships • 4 generally recognized phyla are • CYANOBACTERIA • SPIROCHETES • GRAM-POSITIVE • PROTEOBACTERIA

11. Eubacteria come in three basic shapes: • Bacilli (bacillus): rod-shaped • Cocci (coccus): sphere-shaped • Spirilla (spirillum): spiral-shaped

12. Cell forms: • Diplo- pairs • Strepto: chains • Staphylo: grapelike clusters Identify this

13. Classification by Structure • Eubacteria cell walls are made of Peptidoglycan. • Thickness of cell wall and other membranes protects bacteria against some kinds of antibiotics by preventing their entry into the cell.

14. Gram Stain • Most species of bacteria can be grouped into 2 categories based on their response to a laboratory technique called Gram Staining • Taxonomists divide bacteria into various subgroups including Gram-Positive & Gram-Negative Bacteria

15. Gram Stain • Technique involves staining bacteria with purple dye (Crystal violet) & iodine • Then rinsed with alcohol • Then restained with a red dye (Safranin) • Gram-Positive Bacteria will retain the PURPLE DYE and appear Purple. • Gram-Negative Bacteria will appear RED (pink) from the RED DYE • Depending on cell walls, bacteria absorbs either purple/red dye

16. Gram Stain • Gram-Positive bacteria have thicker layer of peptidoglycan in cell wall • Gram-Positive and Negative differ insusceptibilities to antibacterial drugs, produce different toxic materials, & react differently to disinfectants. Gram + (top), Gram – (bottom) Note: Gram-negative bacteria have cell wall including an outer membrane composed of a layer of lipids and sugars: “glycocalyx”

17. Bacterial Anatomy • Composed of a • Cell Wall • Cell Membrane • Cytoplasm • Some bacteria have distinctive structures, such as flagella, capsules, and outer membranes • Capsule: (glycocalyx) an additional (optional) outer covering; protects against drying or harsh chemicals & host body's white blood cells, which would otherwise engulf (eat) it

18. Structure • Flagella: whip-like structure used for movement • Pili: (pilus) short, hair-like protein structures found on the surface of some species of bacteria  • Help bacteria hold on to host cells & can be used to transfer genetic material from one bacterium to another

19. Structure • Have a single chromosome: DNA in single closed loop • May also have small loops of additional genes: plasmids • Prokaryotes have lots of ribosomes, but no organelles with membranes • Do not have mitochondria or chloroplasts so use cell membranes to carry out cellular respiration or photosynthesis

20. Structure This bacterium has formed an ENDOSPORE • A spore is a dormant structure that is produced by Gram-positive bacterial species that are exposed to harsh environmental conditions. • Cell is encased in a protective covering. • Makes them VERY hard to kill! • When conditions improve they break open & resume producing new bacteria cells Difference between “disinfect” and “sterilize”?

21. Nutrition & Growth • Most Prokaryotes are heterotrophs; get their energy by consuming organic matter as a source of nutrition. • Some are autotrophs; obtain energy by making their own food. • Phototrophs: from sunlight • Chemotrophs: from minerals

22. Bacterial Reproduction • Bacteria cell goal: to grow and multiply • Many can double number every 20 minutes! • Use binary fissionto reproduce asexually, quickly • Process: chromosome is replicated, then the cell divides Binary fission

23. Genetic Recombination Bacteria can also combine genes 3 ways: • Conjugation -- • Transformation (uptake of naked DNA from outside the cell) • Transduction (virus inserts new genes into cell) Conjugation

24. Eubacterial Phyla:

25. Proteobacteria • Nitrogen-Fixing Bacteria • Earth's atmosphere is 80% nitrogen but plants and animals cannot use nitrogen in gaseous state • We require nitrogen to make nitrogen-containing compounds like proteins and nucleic acids • Rhizobium are essential to the nitrogen cycle Legumes have lots of root nodules, filled with these bacteria

26. Cyanobacteria • Gram-Negative bacteria that perform plant-like photosynthesis & release oxygen as by-product (waste) • Once classified as blue-green algae • Now considered eubacteria, because they lack a membrane-bound nucleus & chloroplasts

27. Cyanobacteria • “Eutrophication”: Population Bloom of bacteria = sudden increase in # of cyanobacteria due to high availability of nutrients. • After many cyanobacteria die; decomposed by heterotrophic bacteria. • Consume available oxygen

28. Eutrophication

29. Gram-Positive Bacteria • Actinomycetes: Gram-positive bacteria that form branching filaments; used to make antibiotics.

30. Pros • Used in sewage treatment • Decomposers, breaking down the remains of organic matter in dead plant & animal waste • Recyclers, returning nutrients back to the environment • Food production: Bacteria help us make buttermilk, sour cream, yogurt, some cheese, sauerkraut and pickles http://www.innvista.com/health/microbes/bacteria/foodprod.htm

31. Pros • Industrial chemical production • Help clean up environmental disasters caused by humans, such as chemical & oil spills • Useful in genetic engineering (gene splicing) to produce medicines and drugs.

32. Cons • Spoil food • Cause odor • Some cause illness/disease, death • "Toxins" substances released by bacteria the make you ill

33. Bacteria & Disease • Pathology: scientific study of disease • Pathogens: bacteria that cause disease • Some bacteria cause disease by producing toxins (poisons) • Exotoxins: bacterial proteins; produced by Gram-positive Bacteria • Secreted into the surrounding environment • Tetanus is a disease caused by an Exotoxin. Ever cut yourself or step on a nail and had to take a shot?  That was to prevent Tetanus

34. Bacteria & Disease • Endotoxins: made of lipids & carbohydrates • associated with the outer membrane of Gram-negative bacteria, such as E. coli • Not released until bacteria dies  • Cause fever, body aches, & weakness, & they damage the vessels of the Circulatory System

35. Diseases • Pathogenic bacteria are a major cause of human death and disease and cause infections such as tetanus, typhoid fever, diphtheria, syphilis, cholera, foodborne illness, leprosy and tuberculosis, pneumonia, Lyme disease, etc. • http://biology.clc.uc.edu/courses/bio106/bact-dis.htm • Bacterial diseases are also important in agriculture, with bacteria causing leaf spot, fire blight and wilts in plants, as well as Johne's disease, mastitis, salmonella and anthrax in farm animals. • http://en.wikipedia.org/wiki/Bacterial_diseases

36. Bacteria & Disease • Many antibiotics are derived from chemicals that bacteria or fungi produce; • 3 ways that antibiotics kill bacteria: • interferes with cell wall synthesis, ex: Penicillin • interferes with protein synthesis; ex: Tetracycline • inhibits RNA synthesis; ex: Rifampin • They affect only the growth of bacteria without harming the body cells of humans • Antibiotic Resistance • Overuse of antibiotics encourages drug-resistant strains to evolve through selection • Mutant bacteria continue to grow