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BACTERIA

BACTERIA. Bacteria are microscopic organisms, which come in many shapes and sizes, but even the largest are only 10 micrometres long (1 micrometre = 1 millionth of a metre ). The three most common shapes are: • round (called cocci ) • rod-shaped (called bacilli ) and

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BACTERIA

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  1. BACTERIA Bacteria are microscopicorganisms, which come in many shapes and sizes, but even the largest are only 10 micrometres long (1 micrometre = 1 millionth of a metre). The three most common shapes are: • round (called cocci) • rod-shaped (called bacilli) and • spiral-shaped (called spirilli) • some bacteria also have whip-like tails (called flagella) or hairs (called cilia) which they use to propel themselves along

  2. BACTERIA Bacteria are living cells and in favorable conditions can multiply very rapidly. Inside the body they attack tissues and release poisons or toxins. Diseases caused by bacteria include: • food poisoning, or salmonella • cholera • typhoid • whooping cough • gonorrhea (a sexually transmitted disease)

  3. BACTERIA Despite the variety of shapes they share certain common features:  • they are all microscopic • they have a cell wall but unlike a plant cell it is not made of cellulose; peptidoglycan • they have no nucleus; instead their DNA is dispersed throughout the cytoplasm • they reproduce by binary fission.

  4. BACTERIABinary Fission

  5. BACTERIAConjugation

  6. BACTERIAIdentifying Prokaryote Shapes BacilliCocciSpirilla

  7. BACTERIAIdentifying Prokaryote Shapes

  8. VIRUSES Viruses are: • ultramicroscopicorganisms- many times smaller than bacteria. • Viruses are no more than a fragment of genetic material inside a protective protein coat(capsid). • They have a very high mutation rate which allows them to rapidly evolve into new forms. This makes it harder for their hosts to develop immunity. Chemical 'hooks' and 'drills'

  9. VIRUSES Viruses are strange and scary things. They latch on to a host cell using chemical hooks on their protein coat, and 'drill' through the host cell wall. Once inside, the viral DNA or RNAtakes over the host cell's reproductive mechanism and makes hundreds of thousands of copies of itself. Eventually the virus-clones fill the whole host cell, and burst it open like the baby monsters in the Alien films. The viral offspring are then passed out in the blood stream, the airways or by other routes.

  10. VIRUSES Features common to all viruses are: • all are microscopic; much smaller than bacteria • have genetic material, DNA or RNA, but no nucleus • have a protective protein coat • can only reproduce inside a host cell Viruses can only replicate inside host cells. This makes them difficult to treat as killing the virus also puts the host cell at risk. The best defense against viruses therefore is to stop them getting into the cells in the first place. Common virus pathogens include: • flu • cold • measles • mumps • rubella • chicken pox • shingles

  11. T4 infection E.coli

  12. VIRUSESTobacco Mosaic Virus (TMV)

  13. VIRAL REPRODUCTION • LYTIC CYCLE: in bacterial viruses, the cycle of viral infection, replication and cell destruction.

  14. VIRAL REPRODUCTION • LYSOGENIC CYCLE: During an infection, some viruses stay inside the cells but do not make new viruses. In this cycle the viral genome replicates w/out destroying the host cell.

  15. LYTIC & LYSOGENIC CYCLE

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