Micro-Biology Flashcards
widespread occurrence
- Bacteria are found everywhere in the biosphere
2. Fungi are also very widespread.
Monera
Bacteria
Prokaryotic
have NO membrane bound nucleus and NO membrane bound organelles
Structure and Draw ( bacteria )
- Cell wall: not cellulose
- Slime capsule: helps in resistance (when present)
- Flagellum: For movement (when present)
- Plasmid: ring of DNA; can be exchanged
- Chromosome: loop of DNA; contains genetic information:no nuclear membrane
Classification ( bacteria )
By Shape
(a) Sphere
(b) Rod
(c) Spiral
(ii) Effect of Gram’s Stain: either gram positive (stains) or gram negative (doesn’t stain)
Reproduction ( bacteria )
• Asexual by Binary Fission not mitosis Stages 1. Cell elongates 2. Genetic material replicates 3. Plasmids replicate 4. New cell wall forms 5. Cells separate • Mutations occur occasionally and if these are advantageous then the new strain quickly becomes dominant • In adverse conditions thick-walled resistant endospores produced within the cell
Nutrition
(i) Autotrophic: make their own food by photosynthesis or chemosynthesis
(ii) Heterotrophic: cannot make their own food so are either
a) Parasitic live in or on living organisms causing them harm e.g. tuberculosis
b) Saprophytic : live on dead material causing decay
Factors Affecting Growth
Temperature, pH, O2 concentration, availability of nutrients
Antibiotics
Substances made by micro-organisms that kill micro-organisms
Used to control pathogenic bacteria
• Antibiotics do not have any effect on viruses.
• Pathogenic:
capable of causing a disease
• Antibiotic Resistant and cause
not killed by antibiotics
• Causes:
a) Overuse
b) Failure to complete course e.g. MRSA
Economic Importance of Bacteria: ( beneficial )
Beneficial:
a. Produce antibiotics and
b. Make vitamins B and K in the human large intestine
c. Nitrogen-fixing bacteria in root nodules of legumes
Economic Importance of Bacteria: ( harmful )
Harmful:
a. Cause tuberculosis
b. Streptococcus causing “Strep Throat”
c. Destroy food
Viruses
Difficult to classify because they
- Are non-cellular
- Consist of either DNA or RNA with an outer protein coat
- Are obligate parasites ( can only replicate inside a living host cells )
- Have no organelles
- Do not respire
Viral Replication Stages ( viruses )
- Attachment: virus fits onto sites on the cell membrane of host cell
- Insertion of viral nucleic acid into the host cell
- Uses host structures
- Transcription: making copies of DNA or RNA
- Translation: produce protein coats
- Assembly: joining DNA (RNA) and protein coats
- Release new virus particles by lysis (bursting) cell membrane