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Bacteria

Bacteria. They’re Prokaryotes!. Characteristics of bacteria. The oldest organisms on earth and the most abundant Very diverse as a group but they share some common characteristics: Single-celled All of them are prokaryotes - DNA and cell organelles not surrounded by a membrane

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Bacteria

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  1. Bacteria They’re Prokaryotes!

  2. Characteristics of bacteria • The oldest organisms on earth and the most abundant • Very diverse as a group but they share some common characteristics: • Single-celled • All of them are prokaryotes - DNA and cell organelles not surrounded by a membrane 3. DNA made of one chromosome

  3. Structure

  4. Cell Shape • Coccus(pl. Cocci) – Spherical • Bacillus(pl. Bacilli) – Rod Shaped • Spirillum(pl. Spirilli) – Spiral Shaped

  5. Gram Stain • Classified by their reaction to a purple indicator. (a dye made of crystal violet and iodine) (Caused by a difference in Cell Walls) • Gram +ve (purple) common, not very pathogenic (thick protein layer on the cell wall • Gram -ve (pink) tend to be much more pathogenic (thin protein layer on cell wall)

  6. NutritionHow they obtain energy and carbon to produce organic compounds • Heterotrophs • Most chemoheterotrophs • (obtain energy by breaking down organic molecules from surroundings) • Some parasites • Some Saprophytes (decomposers) • Autotrophs • Photoautotrophs (use energy from the Sun as energy source) • Cyanobacteria • Chemoautotrophs (use the energy of chem. reactions ) • Live in harsh environments.

  7. Respiration • Occurs in the inner surface of the cell membrane of the bacterium ( they lack membrane-bounded organelles) • Produces energy from food that is broken down • Aerobes – use oxygen for cellular respiration • Anaerobes – don’t use oxygen; they use fermentation • Obligate aerobe (if oxygen is absolutely necessary) • Facultative anaerobes – survive with/without O2

  8. Plasmids • In addition to chromosomes, bacteria have smaller ring(s) of DNA containing much fewer genes.

  9. Reproduction • Binary Fission • All bacteria can reproduce by this asexual method • Can divide every 15-20 min in good conditions

  10. Reproduction • Conjugation • Used when survival conditions are not ideal • Type of Sexual reproduction • Two bacterial cells connect by long protein bridges • Plasmid transfers from one cell to the other • The receiving cell undergoes binary fission • Helps change the genetic make up and increase survival rates

  11. Reproduction • Endospore Formation • Used by gram +ve bacteria • In extremely unfavourable conditions • A thick wall is produced around DNA and cytoplasm • Spores are resistant to high temp., freezing, toxic chemicals, radiation, etc. • Spore can remain dormant for months

  12. Disease • Only a small percentage are pathogenic • Disease Causing • Produce deadly substances (toxins) in the human body that cause the disease symptoms i.e. Pseudomonas aeruginosa (Pneumonia)

  13. Antibiotics • Chemicals that inhibit the growth of bacteria or destroy them • Antibiotics are specific (certain types for certain bacteria) • Inhibit cell’s ability to turn glucose into energy • Some inhibit the construction of the cell wall

  14. Classification of bacteria • Bacteria are categorized into 2 kingdoms 1- Archaebacteria – hypothesized to be the ancestors of all kingdoms • Simple organisms • Can inhabit Earth's most inhospitable regions • Can thrive in very hot, very acidic and very salty conditions; scientists think those conditions existed on earth billions of years ago

  15. Archaebacteria • They are categorized into a separate kingdom because: i) The chemical properties of the cell wall and membrane are different from Eubacteria ii) Out of 1700 genes, more than 50% are different from those of eubacteria • Three main phyla of Archaebacteria based on their habitat

  16. Anaerobic methanogens • Mainly live in oxygen-free places (gut of animals, at the bottom of marshes or in depths of landfill sites • They release all of the methane gas found on Earth (1/3 comes from methanogens in the guts of herbivores) • Methanogenesis-an anaerobic process that happens in env. that lack O2 and produces methane (an organic compound) as a by-product

  17. Halophiles and Thermophiles • Halophiles – "salt loving" bacteria that live in extreme salty conditions (salt concentration about 20%), such as the Dead Sea (35%) • Thermophiles – “heat lover” bacteria that can tolerate very hot temperatures; these bacteria inhabit naturally forming hot springs and deep sea vents • Acidophiles – “acid lover” bacteria that can live at a pH of 0 (volcanic crater lakes or mine drainage lakes)

  18. Eubacteria • True bacteria • More successful than archaebacteria, accounting for most of the prokaryotes • Most bacteria are mesophiles- live in environments with moderate conditions • Live in soil and sometimes in other large animals • May infect and produce disease in these organisms, or they may be symbiotic with the organism • Some are photosynthetic

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