Lecture Fifteen - Bacterial structure and function I Flashcards
What is a microbe?
Helps maintain balence of nature.
May be beneficial
Essential to many human processes - food stuffs, antibiotics, biotechnology.
Types of microbes:
Bacteria/archaea - single celled.
Algae/protazoa/fungi - single/multicellular.
Viruses - acellular.
What are the origins of the three domains of life?
1 - last common ancester.
2 - fusion of bacteriaum and archaean.
3 - symbiosis - mitochondrial and eukaryote ancestors.
4 - symbiosis - chloroplast and green plant ancesters.
What are the differences between prokaryotes and eukaryotes?
Structure of nucleus:
Prokaryotic DNA is not surrounded by a membrane.
Prokaryotes have a single circular chromosome - one copy.
Eukaryotes have several linear chromosomes surrounded by a membrane to form a nucleus - two copies.
Cell division - mitosis/meiosis (eukaryotes) vs binary fission (prokaryotes).
Intracellular organelles:
Eukaryotes have membrane bound cellular organelles.
Prokaryotes only have ribosomes.
Cell wall structure:
Bacterial cell wall has many unique compounds - peptidoglycan, lipopolysaccaride, D-amino acids.
How does bacterial binary fission work?
Divide asexually by binary fission.
growth is logarithmic/exponential.
Doubling time for e. coli is about 20 minutes.
What is gram positive and negative bacteria?
Gram positive bacteria have lots of peptidoglycan.
Gram negitive bacteria have an outer membrane, less peptidoglycan and lipopolysaccarides.
What are archaea, and how are they similar and different to bacteria?
Archaea:
Not mechanically important, but useful for other applications (e.g. PCR).
Extremophiles (high temperatures, high acidity etc.).
Closest to univeral ancestor.
Four main groups of archaea - methanogenes, thermophiles and halophiles.
Two part names - first word = genus, second word = species.
Similarities between bacteria and archaea:
Hereditary mechanisms (cell division).
Cell membrane composed of lipids.
Cell wall.
ATP-based metabolism.
Differences between bacteria and archaea:
No peptidoglycan.
Unusual lipids in cell membrane.
Eukaryoteic not prokaryotic gene structure.
Eukaryoteic not prokaryotic ribosome structrure.
How can bacteria be grown in the lab?
Liquid media - broth = inoculation.
Solid media - agar = streaking.
What is a gram stain and how does it work?
First step towards the ID of an unknown bacteria - differential staining techique.
Differentiates between gran +ve and gram -ve.
Describe microbial interactions with hosts.
Human body can provie a favourable nevironment ofr bacterial growth - rich source of nutrients, a stable temperature, pH and physical environment at a particular site (niche).
Bacteria found in the body sites that are in contact with the outside world - e.g. skin, digestive tract, anus etc.
There are 10 times from microbial cells in and on our body comparted with our own body cells.
Most bacteria have little or no effect on the host.
Some bacteria are able to cause damage/harm to the host 0 these are pathogens.
The severity of damage is a measure of pathogenicity or virulence of a bacterial sp.
Infection - refers to the growth of bacteria (or other microbes) in or on a host.
Initial inoculation rarely sufficient to cause damage.
Pathogen multiplication after access to the body.
bacteria must find approprate miche.
Infection does not necissarily = disease.
Disease = injury to host that imparis host’s function.
Colonisation = infection, usually of normal flora.
To colonise a host and microbe must: Enter the body, adhere to a body surface, survive in the host, multiply and disseminate, then cause damage to the host (pathogens only).
