Bacterial and Fungal Human Pathogens & Lifecycles Flashcards
What are the main bacterial shapes?
Cocci (spherical), Bacilli (rod-shaped), Vibrios (comma-shaped), Spirochetes (spiral, e.g., syphilis).
How is bacterial morphology determined?
By growing bacteria on agar or using a light microscope.
Why is bacterial morphology important?
Helps identify bacteria and determine the best treatment.
What are the phases of bacterial growth in liquid?
Lag phase – No growth, bacteria adapt.
Log phase – Rapid exponential growth.
Stationary phase – Growth and death rates equal.
Death phase – Bacteria die exponentially.
Why is the bacterial cell wall important?
Essential for survival, protects against osmotic pressure, and is a target for antibiotics, immunity, and diagnostics.
What are the differences between Gram-positive and Gram-negative bacteria?
Gram-positive: Thick peptidoglycan, contains teichoic acid, stains purple.
Gram-negative: Thin peptidoglycan, outer LPS membrane, stains pink.
What are the main fungal forms?
Yeasts (unicellular), Moulds (filamentous), and Polymorphic fungi (switch forms).
What is the fungal cell wall made of?
Chitin and glucan (strength), mannan (outer layer)
How do fungi reproduce?
Asexually (budding, spores) and sexually
How do bacterial and fungal infections enter the body?
Through specific entry sites; fungi are not transmitted via arthropods.
What influences the severity of fungal infections?
The host’s immune system; fungal infections are often opportunistic
What are common bacterial infections?
Meningitis, pneumonia, skin infections, eye infections, sinusitis, UTIs, gastritis, food poisoning.
What are common fungal infections?
Superficial – Thrush, dandruff, athlete’s foot.
Subcutaneous – Rare, black moulds, madura foot.
Invasive – Affects immunocompromised people (e.g., fungal meningitis).
What are the steps of bacterial and fungal infections?
Finding – Opportunistic infection.
Adhering – Using adhesins (capsules, pili, cell walls).
Colonisation – Growth and establishment.
Multiplication – Reproduction within the host.
Evasion of host defences – Avoiding immune response.
What is biofilm formation?
A protective microbial community with four stages: Attachment → Initiation → Maturation → Dispersal
What is an adhesin?
A bacterial ligand that allows adhesion to host tissues
How do fungi invade tissues?
Enzymes (proteinases) degrade host tissues.
Hyphal growth enables penetration
How do bacteria survive inside phagocytes?
By avoiding immune detection, using host nutrients, and resisting antimicrobial defences.
Why is fungal polymorphism important?
Many fungal pathogens switch forms to evade immune responses and increase virulence.
What are the basic types of viral structures?
Helical (± envelope)
Icosahedral (± envelope)
Complex
What is the difference between naked and enveloped viruses?
Naked – Only nucleocapsid (capsid + genetic material).
Enveloped – Nucleocapsid + lipid membrane with glycoproteins.
What are the steps of viral infection?
Attachment → Penetration → Uncoating → Biosynthesis → Assembly → Release.
How does influenza infect cells?
Hemagglutinin binds to sialic acid on host cells.
Virus enters via endocytosis.
RNA replication and protein synthesis occur.
New viruses assemble and leave by budding.
What are bacteriophages?
Viruses that infect bacteria.
What are the two types of bacteriophage life cycles?
Lytic – Immediate bacterial destruction.
Lysogenic – Viral DNA integrates into the host genome before activation.
What are the main steps of infection?
Adhesion → Colonisation → Invasion → Evasion of host defences.
Why is the cell wall important?
It interacts with the extracellular environment and is a target for therapeutics.
How do bacterial and fungal morphology affect infection?
Morphological changes help pathogens adapt, survive, and invade the host
