TOB Session 4 Flashcards
Bacteria and Viruses
What is infection?
The multiplication / colonisation of a pathogenic microbe in a susceptible host with associated dysfunction/damage.
What causes infection?
Pathogenic microbes. The agent must be shown to be present in every case of the disease by isolation in pure cultre. The agent must not be found in cases of other disease. It must be capable of producing disease on its own. NECESSARY & SPECIFIC.
Why are some people more susceptible to infection than others?
- Weakened immune system
- Poor nutrition
- Poor living conditions
- Bad healthcare
- Genetic predisposition
- Lifestyle
What three things influence the outcome of an infection?
- The immune system of the host
- The affected body system(s)
- Drugs/antibiotics used
Compare and contrast bacteria and viruses.
Bacteria do not have capsids, Viruses can have capsids.
Neither bacteria nor viruses have membrane bound organelles.
Bacteria can have pili or flagella, viruses do not.
Viruses can have reverse transcriptase, bacteria do not.
Bacteria have circular DNA as well as RNA, Viruses have either one.
What are the differences and similarities between bacteria and eukaryotes?
Bacteria have peptidoglycan or lipolysaccharide cell walls, eukaryotes have no cell wall.
Neither bacteria nor eukaryotes have a capsid.
Eukaryotes have membrane bound organelles, bacteria do not.
Eukaryotes have a nucleus, bacteria have circular DNA.
Bacteria have pili or flagella, eukaryotes do not.
Neither has reverse transcriptase.
Describe the differences and similarities between eukaryotes and viruses.
Viruses do not have organelles, eukaryotes do.
Viruses can have capsids, eukaryotes cannot.
Viruses have DNA or RNA, Eukaryotes have both.
Neither have pili or flagella
Viruses can have reverse transcriptase, eukaryotes cannot.
What is a Gram Stain?
Gram stains let us detect and classify most bacteria as Gram positive or Gram negative.
What colour do Gram stains stain?
Gram negative bacteria stain red whereas Gram positive bacteria stain blue.
How does a Gram stain work?
Positively charged crystal violet binds to negatively charged cell components. It then forms a large molecular complex with iodine when added. Acetone or methanol extract the complexes through Gram negative cell walls but not through gram positive cell walls. A red dye is then used to stain the unstained Gram negative cells.
What are acid fast stains for?
They allow us to detect the bacterial causes of TB and leprosy (mycobacteria) as this kind of bacteria cannot be gram stained.
What is a pathogen?
A bacterium, virus or other microoganism that can cause disease.
Why are RNA viruses more likely to mutate?
Because RNA is less stable than DNA
How does an envelope affect the survival of a virus?
Viruses with envelopes are more easily sterilised as when holes are punched in the envelope the virus cannot survive.
What are the three ways by which a virus can replicate?
RNA viruses use reverse transcriptase, DNA viruses use cell machinery or other viruses carry their own replication enzymes.
Name three DNA enveloped viruses and describe the conditions they cause.
Hepatitis B causes inflamed liver
Herpes causes oral/genital herpes
Smallpox virus causes smallpox
Name one DNA non-enveloped viruses and describe the condition it causes.
HPV virus causes Warts & cervical cancer
Name four RNA enveloped viruses and describe the conditions they cause.
HIV causes AIDS
Rubella causes Congenital Rubella Syndrome
Rotavirus caused Diarrhoea
Corona virus causes SARS
Name two RNA non-enveloped viruses and describe the conditions they cause.
Polio causes inflammation of the spinal cord
Hepatitis A causes Liver disease.
List two gram positive cocci
Staphylococcus
Streptococcus
What do the following types of bacteria look like? a) Staphylococci b) Bacilli c) Streptococci d) Diplococci
a) Clusters of circular bacteria
b) Rod shaped bacteria
c) Chains of circular bacteria
d) Pairs of circular bacteria
Name one gram negative cocci
Neisseria
Name one Gram positive bacilli
Clostridium
Name six Gram negative bacilli
Escherichia Salmonella Helicobacter Pseudomonas Leigonella Bacteroides
