Bacteria

1. Bacteria Marconi 2007

2. Bacteria consist of only a single cell, but don't let their small size and seeming simplicity fool you. They're an amazingly complex and fascinating group of creatures. Marconi 2007

3. Builders of Modern Life • Bacteria are among the earliest forms of life that appeared on Earth billions of years ago. • Bacteria helped shape and change the young planet's environment, eventually creating atmospheric oxygen that enabled other, more complex life forms to develop. Marconi 2007

4. What are bacteria? • Bacteria are unicellular, living things. • Prokaryotic cells (without a nucleus). • Obtain nutrients is different ways: • Photosynthetic autotrophs- convert inorganic molecules into sugar using sunlight • Heterotrophs- consume food by growing on it • Saprophytes- obtain food by decomposing dead material • Chemotrophs- manufacture organic compounds from inorganic compounds such as hydrogen sulfides Marconi 2007

5. Bacteria feeding on saguaro Cyanobacteria in a lake Bacteria used in wastewater treatment Chemotrophs at hydrothermal Vent Marconi 2007

6. Marconi 2007

7. Marconi 2007

8. Classification of Prokaryotes • All prokaryotes belong to the kingdoms: • Archaea • Eubacteria Marconi 2007

9. Archaea • First discovered in 1970’s • Discovery made the term “Moneran” obsolete • Biochemically different from eubacteria • May have evolved in the harsh conditions of early Earth • They are abundant in, but not restricted to, extreme environments because of their ability to withstand the harshest of environments • May be the early ancestors of eubacteria Marconi 2007

10. Characteristics of Archaea • Archaea (Formerly Archaebacteria) • Lack an important carbohydrate (peptidoglycan) found in the cell wall of nearly all Eubacteria. • Live in harsh environments • Oxygen-free environments • Methanogens (ex. Thick mud & digestive tracts) • Produce methane gas • Salty environments • Extreme Halophiles • Great Salt Lake/Dead Sea • Hot Springs • Thermoacidophiles Marconi 2007

11. Characteristics of Eubacteria • Eubacteria = Modern Bacteria • Unicellular • Cell walls contain peptidoglycan • Genes lack introns • Reproduce asexually by binary fission • Either autotrophic or heterotrophic • Extremely diversified groups • Certain types may be ancestors of mitochondria Marconi 2007

12. Bacterial Shapes Bacillus = Rod Coccus = Round Sprillium = Spiral Colony growth Cells arranged in particular ways Form long chains Grow in clusters Bacterial movement Flagella Some do not move Some glide Identifying Prokaryotes Marconi 2007

13. Shape #1 is rod shape, also known as bacillus. Marconi 2007

14. Shape #2 is sphere shaped, also known as coccus. Marconi 2007

15. Shape #3 is spiral shape, also known as sprillum Marconi 2007

16. Micrococcus luteus tetrad Bacillus cereus Vibrio Rhodospirillum Marconi 2007

17. Bacterial Structures • Cell Wall- support and protection • No nucleus- Bacterial DNA is usually coil-shaped and not enclosed in a nuclear membrane. • Most bacteria also have small ring-shaped pieces of DNA called plasmids • Capsule- protective layer that surrounds the cell • Some have flagellum to aide with movement • Pilus aides in adhesion to other cells Marconi 2007

18. Marconi 2007

19. Bacterial growth and reproduction • Grow and reproduce at an incredible rate when conditions are favorable • Bacterial growth stays under control due to limiting factors such as nutrient availability and production of waste products. • Reproduction methods • Binary fission • Conjugation Marconi 2007

20. Binary fission • Asexual reproduction • When a bacterium is almost double in size, it replicates it’s DNA and divides in half. • Example: E. coli Marconi 2007

21. Conjugation • Sexual reproduction • Long bridge of protein in between 2 bacterial cells connecting them. • Genetic material from donor cell is transferred to the other cell. • Recipient cell ends up with different combo of genes. • Leads to genetic variation, evolution, antibiotic resistance Example Marconi 2007

22. Spore formation • Spores form when conditions become unfavorable. • Endospore is a type of spore that forms a thick internal wall that protects the DNA and cytoplasm. • Endospores can remain dormant for months to years while waiting for favorable conditions to arise. Marconi 2007

23. Why are bacteria important? • Food production • Yogurt, cheese, buttermilk, sour cream, pickles • Used in industry • Digest petroleum; clean up oil spills • Used in mining • Used in sewage treatment plants • Symbiosis • Digestion • Nitrogen-fixation and plants Marconi 2007

24. Downside of bacteria • Pathogens • Disease causing agents • Small number of bacteria are pathogens • Examples of pathogenic bacterial infections: • Syphilis, cholera, tuberculosis, bubonic plague, botulism, tetanus, gingivitis, strep throat • Pathogens cause disease by: • Damaging cells and tissues for use of nutrients • Release toxins Marconi 2007

25. Marconi 2007

26. Treating bacterial infections • Antibiotics destroy bacteria by disrupting the structure of the cell wall • Over prescribing of antibiotics is causing antibiotic resistance because bacteria mutate readily Marconi 2007

27. Bacterial respiration • Energy is supplied by respiration and fermentation • Respiration involves oxygen and breaks down food molecules to release energy • Fermentation is energy production without oxygen • Obligate aerobes • Bacteria that require a constant supply of oxygen • Obligate anaerobes • Must live in the absence of oxygen • Example: Clostridium botulinum • If subjected to air and allowed to grow on food, it will produce toxins that cause severe food poisoning. • Facultative anaerobes • Can survive with or without oxygen • Allow facultative anaerobes to live almost anywhere. Marconi 2007

28. The End Marconi 2007