Week 6 Flashcards
What is the term for the genetic material present in bacteria?
Nucleoid
Describe the nucleoid of bacteria
One chromosome
No nuclear membrane
Do bacterial cells have a nuclear membrane?
No
How many chromosomes do bacteria have?
1
What are the chemicals present in bacterial cell walls?
Peptidoglycan
N-acetyl glucosamine
N-acetyl muramic acid
Describe the structure of peptidoglycan
Alternating chains of NAM and NG which are linked by peptide chains
In what types of bacteria are the peptide links between alternating chais of NAM and NG in peptidoglycan of cell walls different?
Gram positive and gram negative
Describe the outer membranes of gram positive bacteria from the inside out
Internal membrane, periplasm which has a peptidoglycan layer, outermsmbrane of lipopoylsacchardes and proteins.
In which region of gram negative bacteria is the peptidoglycan present?
In the periplasm
What is contained in the outer membrane of gram negative bacteria?
Lipopolysaccharides and proteins
Describe the membranes of gram positive bacteria
Internal membrane and peptidoglycan outer layer
Describe the thickness of the peptidoglycan layer in both gram negative and gram positive bacteria
Gram -ve = think
Gram +ve = thick
What colour do gram positive bacteria appear under a light microscope after gram staining?
Purple
Describe the thickness of the cell wall of gram positive bacteria
Thic
What are the major components of the cell walls in gram positive bacteria?
Teichoic acid
Peptidoglycan
Describe the outer membrane of gram positive bacteria
No outer membane
What colour do gram negative bacteria appear after gram staining?
Pink
Describe the thickness of the cell wall of gram negative bacteria
Thin
Which type of bacteria have teichoic acid in their cell wall
Gram positive only
What are the purpose of lipopolysaccharides in the outer membrane of gram negative bacteria?
They aid pathogenicity
Describe the permeability of the cytoplasmic membrane of bacterial cells
Selectively permable
What is the site of cellular respiration in bacterial cells?
Cytoplasmic membrane
What is the purpose of the cytoplasmic membrane in bacterial cells?
Site of respiration.
Transports nutrients, waste and proteins.
Where are the cellular receptors found in bacterial cells?
Cytoplasmic membrane
Which ribosomes are present in Prokaryotes and Eukaryotes ?
Pro - 70s
Eu - 70s (in organelles) and 80s
What are plasmids?
Extra chromosomal pieces of DNA that can replicate independently of the bacterial chromosomes.
What are the 2 types of sugar coating that can surround bacterial cells?
Slime layer
Capsule
Describe the association between a slime layer or a capsule with a bacterial cell
Slime layer - loose association
Capsule - tightly bound
What are the fimbriae of bacteria?
Thin, straight, protein appendages which are involves in pathogenesis
What are specialised bacterial fimbriae called?
Pilli
What are bacterial pills?
Specialised Fimbriae which are involved in the genetic material from cell to cell
What is the main function of bacterial flagella?
They are responsible for motility
What are the different types of flagella?
Peritrichous
Polar
Lophotrichous
What are Peritichous flagella?
Flagella all over the bacterial surface
What are Polar flagella?
One or more flagella at one or both ends of the cell
What are Lophotrichous flagella?
Multiple flagella at the same point on the bacterial surface
What type of bacteria produce endospores?
Gram positive
Describe the thickness of endospore cell walls
Thick
Describe the water content of bacterial endospores
Very little water contained
How long can bacterial endospores survive?
Up to 300 years
What happens when a bacterial endospore is stimulated to return to a vegetative state?
The enzyme cortex is digested.
Core rehydrates.
Nutrients are taken up.
What are the types of endospore locations
Terminal
Subterminal
Central
What are subterminal endospores?
They are located between the middle and the end of a vegetative cell
On what type of cells are bacterial endospores present?
Vegetative
Outline the Sporulation cycle of a vegetative cell.
Chromosome is duplicated and separated.
Cell is separated into Sporangium and Forespore.
Sporangium engulfs forespore.
Sporangium begins to actively synthesised spore. layers around foreshore.
Cortex and outer coat layers are deposited.
Mature endospore formed.
Free spores are released with loss of the sporangium.
Germination of spore swells and releases vegetative cell.
What are the chemical requirements for microbial growth?
Carbon Hydrogen Nitrogen Phosphorus Sulphur Trace elements Sometimes oxygen
What are trace elements?
Minerals present in living tissues in small amounts
What are heterotroph organisms?
Use organic carbon source
What are autotroph organisms?
Use carbon dioxide as their primary carbon source
What are the 2 classifications of microbes based on their energy source?
Chemotrophs
Autotrophs
What are growth factors in terms of microbes?
Any compound which an organism requires for growth but cannot synthesise itself.
Give examples of microbe growth factors
Amino acids
Vitamins
Haemins
What is meant by water activity in terms of microbes?
The availability of water for use by a microorganism
What are the cardinal temperatures of a microorganism?
The minimum, optimum and maximum temperatures at which each organism can grow
What are extremophile microbe?
Organisms which can live in extreme tempeatures
Describe the temperatures at which Psychrophiles live
Optimum temp of 15 degrees Celsius. Minimum temp = 0 degrees Celsius
Describe the temperatures at which Psychotrophs live
Optimum = 20 degrees celsius Max = 40 degrees celsius
Where in the world are Psychrophiles most likely to be found ?
In the poles
Describe the temperatures at which Mesophiles live
Optimum 37-40 degrees celsius.
What type of bacteria (in terms of temperature) are commensal floral bacteria categorised into?
Mesophiles
Describe the temperatures at which thermophiles live
Optimum = 60 degrees celsius
What are Halophile microbes?
They can tolerate saline (stay) solutions and require a certain amount of salt for growth
What do Halophiles require for growth?
Salt
What is meant by ‘Halotolerance’?
The ability of a microbe to grow at a higher salt concentration than there optimum.
What are Osmophile microbes?
They are able to tolerate sugar solutions
What are Xerophile microbes?
They are able to tolerate dry solutions
Not all microorganisms require oxygen , but what do they definitely require?
An electron acceptor
What are obligate aerobe microbes?
Can only grow if oxygen is present
What are obligate anaerobe microbes?
Do not grow in oxygen. May be poisoned by oxygen
What are facultative anaerobes?
Do not require oxygen, but grow better if it is present
What are Microaerophiles?
Require a specific reduced level of oxygen to survive and grow.
What are Aerotolerant Anaerobes?
Grow equally well with or without oxygen
What is pH a measure of ?
Concentration of H+
What are acidophiles?
Organisms which will grow in acid environments
What are Alkalophiles?
Organisms which will grow in acidic environments
What pH do most bacteria grow at?
6.5-7.5
What pH do most yeast grow at?
5-6
Overall, what are the factors affecting microbial growth?
Temperature, water availability, oxygen availability, salt levels, pH
