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
viruses shapes
rod
spherical
complex
Economic and Medical Importance of Viruses
harmful and beneficial
Many workdays and crops are lost due to viral diseases
Harmful:
a) Foot and Mouth,
b) Tomato (tobacco, potato) mosaic virus,
c) HIV (AIDS), and HPV ( genital wart virus) cause cervical cancer
Beneficial:
(a) Bacteriophages can be used to control pathogenic bacteria
(b) Biological control: e.g. myxomatosis and rabbits
(c) Vector in genetic engineering
Protista
Amoeba
• Eukaryotic
have a nucleus and membrane bound organelles
• Nucleus
control centre of cell
• Contractile Vacuole
for osmoregulation it is active in fresh water to stop amoeba bursting as water continually moves in due to the contents being hypertonic [more concentrated] to the surrounding water
• Pseudopodia
(i) for movement
(ii) engulfing prey by phagocytosis
• Food Vacuoles
digest food mainly bacteria
Undigested food is egested
Reproduces ( amoeba )
binary fission
Growth Curves of Micro-organisms
- Lag – no reproduction - adapting to a new environment
- Log – fast reproduction – no competition – plenty of resources
- Stationary – increased competition for nutrients - toxic waste build-up
- Decline – death rate increasing – lack of resources – toxic waste build-up
- Survival by endospores or death
- Bioprocessing
* Bioreactor
use of cells or enzymes to produce useful substances
vessel in which products are made by cells or organisms
Batch and Continuous
BATCH
• Fixed amount of nutrients added at beginning
• Products removed at end of production
• Vessel cleaned to start again
• E.g. using lactobacillus in cheese making
CONTINUOUS
• Nutrients continuously fed into one end of bioreactor
• Product removed continuously from other end
• Over a long period of time
• e.g. using yeast to make industrial alcohol
Yeast ( cycle )
- Unicellular Fungus
- Yeast reproduces asexually by budding
- Nucleus divides by mitosis
- One nucleus moves into the bud
- Bud is pinched off forming a new cell
yeast budding structure
cell wall cell membrane bud cytoplasm nucleus vacule
amoeba structure
cytosplasm ( ectoplasm / endoplasm ) nucleus bacteria pseudopodia food vacule contractile vacuole
