1. Prokaryotes Lack nuclei Typically lack or have very few internal membranes Cytoplasm contains ribosomes, storage granules that hold glycogen, lipid, or phosphate compounds Metabolic enzymes are associated with the plasma membrane, especially where it is infolded to form limited internal membranes – such membranes are generally referred to as a mesosome The plasma membrane interacts with the cytoplasm in signaling functions Motile bacteria have a corkscrew flagellum

2. Prokaryotic Organization Key features –No nucleus –DNA held in nucleoid –Cytoplasm dense: Ribosomes Storage granules Limited membranes –Plasma membrane –Corkscrew flagellum –Cell wall is complex Outer membrane Peptidoglycan layer Capsule Pili extend from cytoplasm

3. Domains of Life

4. BACTERIA ARCHAEBACTERIA –Introns in DNA –Lack peptidogycan in cell walls –Live in extreme environments EUBACTERIA –Includes most bacteria –Most have one of three shapes –May be divided into up to 12 phyla –Classification is controversial

5. Archaebacteria and Eubacteria Carl Woese has indicated, based on small subunit ribosomal RNA (SSU rRNA) sequencing, that there are two domains of bacteria Archaea –Lack peptidoglycan in cell wall –Produce methane gas –Ether-linked lipids –Live in ‘early Earth’ conditions –Extreme halophiles, thermophiles, and acidophiles Eubacteria –Have peptidoglycan in cell wall –Are rifamycin-sensitive (blocks transcription) –All other bacteria

6. TYPES OF ARCHAEBACTERIA Thermoacidophilies Living in hot springs Methanogens living in sewage Extreme halophile living in the Great Salt Lake

7. The Archaea Methanogens –Anaerobes –In digestive tracts of animals –Produce methane gas Extreme halophiles –Live in saturated salt –Many are photosynthetic Extreme thermophiles –Live in hot springs –Often live in acidic environments (acidophiles)

8. The Eubacteria Most abundant bacteria Important in the biosphere –Major producer of primary production (of carbon via photosythesis) –Most numerous organisms in the soil –Most important nitrogen fixing organisms, often via symbiotic associations e.g. rhizobial bacteria in root nodules

9. Bacteria Bacteria are prokaryotes –They are cells –They lack nuclei There are two professional viewpoints regarding the general, overall classification of prokaryotes: –Some biologists support the concept that they constitute two domains: Archaea and Eubacteria –Other biologists classify them into two kingdoms, Archaebacteria and Eubacteria Most are very small – 0.5 – 1.0  m in diameter

10. BASIC SHAPES OF EUBACTERIA SPHERICAL ROD-SHAPED SPIRILLA

11. Cell Walls Provides support for cell Protects against osmotic shock –Most bacteria well adapted to hypotonic conditions –Most bacteria grow poorly in hypertonic conditions; hence jams, salted foods prevent bacterial growth Cell wall composition unique to bacteria –Eubacterial cell wall made of peptidoglycan Complex of polymerized amino sugars and short polypeptides Is really one polymer surrounding the cell

12. Capsules and Pili Many bacteria secrete a capsule, or slime layer –Used to attach, prevent phagocytosis –Can be used to enhance infective bacteria Pili are hair-like appendages –Allow attachment to surfaces –Are sometimes involved in bacterial conjugation (sexual activity that involves the transfer of DNA)

13. The Bacterial Flagellum Rotates Is corkscrew-shaped Three parts: –Basal body –Hook –Filament (made of one protein: flagellin) Cell uses ATP to pump protons out Protons diffuse through membrane at basal body Breakdown of gradient converted to rotation

14. The Gram Stain Bacterial cell wall differences can be used to identify and categorize cells 1888: Christian Gram developed the Gram Stain –Some bacteria retain crystal violet stain after alcohol wash Called gram-positive –Other cells referred to as gram-negative Stain retention determined by cell wall organization –Gram-positive cells have thick peptidoglycan wall –Gram-negative cells have outer membrane and thin peptidoglycan layer

15. Gram-positive and Gram-negative Cell Walls

16. Most Species of Eubacteria may be Grouped Based on Staining Gram-Negative –Lack thicker layer of peptidoglycan –Stain pink –Endotoxins Gram-Positive –Thicker layer of peptidogycan –Stain purple –Exotoxins (released when bacteria die) Gram- negative Gram-positive

17. Giant Bacterium But size is not an indicator; Epulopiscium fishelsoni is a giant bacterium from the gut of the surgeonfish Here, ~ 600  m long and 80  m wide, much larger than the large protist Paramecium (other cells in picture)

18. Nutrition and Growth Saprophtesex: decomposers Photoautotrophsex: blue-green algae Obligate anaerobes ex: tetanus Facultative anaerobesex: E.Coli Obligate aerobesex: tuberculosis Thermophilic bacteria Most bacteria grow at at neutral pH but some grow best at a pH of 6 or lower –Bacteria that produce yogurt and sour cream

19. Anabaena: a Eubacterium Complex, free-living & photosynthetic A cyanobacterium The larger cells fix nitrogen, are oxygen-sensitive

20. Bacterial Chromosome Bacteria have a circular genomic DNA molecule - –Single chromosome –~1000X longer than cell if stretched out Also have plasmids –Small, circular DNA fragments –Can replicate independently of the genomic DNA or be integrated into genomic DNA –Carry genes for resistance, for genetic exchange or for enzymes

21. Bacterial Sexual Reproduction Most simply put, sex is transfer of genetic information. Three mechanisms known for bacterial sexual reproduction: –Transformation Bacteria take up DNA from environment Griffith’s 1928 experiment with S and R bacteria showed that DNA was heritable substance –Transduction Genes are transferred through phage (next slide) –Conjugation Two cells of opposite mating type come together, form pili bridges bridges through which DNA is transferred

22. Conjugation of E. coli

23. Bacterial Pathogens Some are disease-causing agents –Most bacteria are not harmful –Many have positive relationship with hosts – e.g. human gut microbe E. coli –But many are pathogenic –Cause serious disease: Cholera Diphtheria Tuberculosis

24. Antibiotics Antibiotics are drugs that combat bacteria by interfering with cellular functions –Penicillin – interferes with cell wall production –Tetracycline – interferes with protein production –Sulfa drugs – produced in the laboratory –Broad-spectrum antibiotics will affect a wide variety of organisms

25. Endotoxins Pathogenic bacteria can produce exotoxins, which increase their success but tend to be very damaging to the host –Often the toxin, not the bacterial infection, is most dangerous –Examples: Diphtheria toxin Botulism toxin Endotoxins: –Not secreted but are components of the cell wall –Affect host when released from dead bacteria –Can bind macrophage, cause the release of fever- inducing agents –Resistant to heating

26. Commercial Bacteria Bacteria used in many commercial processes –Lactic acid bacteria convert lactic acid to simpler monomers Used in yogurt, acidophilous milk for lactose-intolerant people –Bacteria used for making Cheeses Fermented meats such as salami Pickling agents such as vinegar –Bacteria also used to make pharmaceutical agents –Also used as means to make biomedical agents and biological molecules –Used also to reduce pollution – as bioremediation agents

27. Penicillin This amazing fungus produces the famous antibiotic, penicillin. In 1928. Alexander Fleming observed that a mold called Penicillium notatum produced a substance, later known as penicillin, that killed bacteria in its presence. This antibiotic was the first of many to be found and used to treat infections. Interferes with cell wall production. This fungus makes antibiotics and cheese. Other varieties of the fungus produce blue cheese and Roquefort cheeses.

28. Koch’s Postulates Robert Koch, late 19 th Century Defined conditions likely to identify a pathogen 1.Present in all infected individuals 2.Sample of the micro organism can be grown in culture from the host 3.Culture produces disease in a second host 4.Microorganism can be recovered from second, experimentally created host