L4 - Bacterial function - changing the external environment Flashcards
how does bacteria change their external environment?
- through metabolic activities (consume nutrients release waste product)
- through secretion of proteins and chemicals (nutrition, competition, habitat, motility)
What is metabolic output? give some examples and how does it change external environment
external accumulation of secreted metabolic products and by products. - bacteria is very good at output so it accumulates lots of waste product → as a result change the chemistry of their environment
- e.g. fermentation is the accumulation of alcohol
- e.g. lactic acid produced at high conc → detrimental to their own growth
what are metabolic inputs
consumption of nutrients and compounds from their environents
What is bioremediation
uses microorganisms to clean up contaminated soils and ground water bc bacteria uses contaminants as source of food and energy. so they break down hazardous substances into less toxic substances
example of bioremediation
bacteria uses inorganic chemicals as electron acceptors for metal decontamination and produces byproducts such as CO2 nitrogen and methane
to consume nutrients, bacteria needs to transport nutrients from growth medium into cytosol. what are the 3 modes of transport
simple transport, group translocation, ABC transport
gram =ve has 2 membranes. how do substrates cross the outer membrane?
porins
describe simple transport
crosses transmembrane protein driven by proton motive force. transports smaller molecules and ions
what are the 3 types of simple transports
uniport = one
anti port = same time but one goes in one goes out (simple transport, proton goes in, molecule comes out)
symport = same time same direction
describe group translocation
- transports sugars
- multiple proteins involved
- chemical modification of the substance
- driven by energy rich organic compound
describe ABC transport
- ABC = ATP binding casette
- perplaasmic binding proteins involved (gram negative)
- energy from ATP
- larger molecules e.,g. sugars, AA< inorganic nutrients
how are waste products secreted into external environment?
reflux pumps to remove waste products
What is a signal peptide and how does it gets transported?
15-20 AA at the n terminal in the AA sequence single sequence, it tells them that it should not be folded but transported to the membrane and exported (periplasm or outer space). cleaved to become mature protein. through cytoplasmic membrane translocases
to insert or export proteins (e.g. Sec pathway). gram negative 2 step process
what is the type 3 secretion system?
pathogenic bacteria use injectisomes to
deliver toxins directly into host cells. - transports proptein from cytosome into host cell via cell-cell contact
- syringe like mechanism
- embedded in plasma membrane and crosses outside (injectisomes)
Why does the Type 3 Secretion System (T3SS) require many different genes?
The injectisome must transfer multiple effector proteins into host cells, requiring many genes to encode these components.
How is the expression of T3SS genes regulated?
T3SS genes are controlled by an inducible promoter, meaning they are only expressed under specific conditions. The injectisome is only expressed when induced by a small molecule, ensuring bacteria conserve energy until secretion is needed.
What is the function of the Type VI Secretion System (T6SS)?
T6SS is a molecular weapon used by bacteria to inject toxic effectors into competing microbes or host cells. cross bow like, as tube contract it ejects tube into target cell
When do bacteria use the Type VI Secretion System (T6SS)?
T6SS is used during bacterial niche competition to eliminate rivals and secure resources.
How does T6SS help bacteria invade and compete in an environment?
Bacteria use T6SS to inject toxic effectors into competing microbes, weakening or killing them to dominate the niche.
How does E. coli use T6SS against pathogens?
A: E. coli employs a needle-like structure to inject a tube into target cells, delivering toxins to outcompete pathogens.
Nutrition: why do bacterias secrete hydrolyses?
to break down complex molecules ( such as cellulose) into smaller compounds
What is the function of the cytophaga?
secrete enzymes from cell into cellulosome → degrades cellulose into smaller chunks that can be imported into cell
Competition: how does bacterial antibiotics work?
inhibits protein synthesis by targeting ribosomes and others degrade the cell wall
What are bacteriocins?
kill strains of the same or closely related species bind to receptors on sensitive cells and penetrate through plasma membrane
How is T/AT system used for preventing biocontainant?
- toxin can harm bacterial cell
- cells produce both antitoxin and toxin
- antitoxin binds to toxin
- creates system for cells to survive in contained environment but die in open environment
What is the T/AT system?
- in lab = add smt to growth medium that stops toxin production so number of toxin and antitoxin is the same and cancels out
- in environment = more toxin and not enough antitoxin so cell death is brought about
why does bacteria find its habitat and builds its own niche?
- use chemotaxis to find niche for correct environment
- they adhere to surface once niche is found
surface niches: saves energy’s greater access to nutrients and protection from predation
adhesion through: cell surface proteins, pili, capsule
What are biofilms and what are its benefits
biofilms = most common mode of bacterial growth. cells glued together by slime (can ind yeast within biofilm)
- physical = protection from shear stress
- chemical = adsorption of nutrients, microniches with optimum parameters
- biological = local release of extracellular enzymes
Biofilm lifecycle, planktonic vs sessile cells
- cells have flagella and transport
- attatch when found good niche
- lose their flagella and start producing more slime and multiply
- as they grow, they produce more slime and eventualy become mature columns
- so big compared to cell size that inside column, oxygen and other nutrients are depleated
- cells on the centre change and transform back to planktonic state
- columns burst and release plantktonic cells to them make new colonies
What happens to antibiotic resistance under biofilms
bacteria becomes less susceptible to antibiotics
how are biofilms used in the industry?
- biofilm fouling → cooling systems
- biofilm reactor → waste water treatment
What is swarming?
- collective behaviour characterised by high cell density, secretion of surfactants (decrease surface tension)
- migration in packs within a thin liquid layer super diffusive cell motility
- edges of colonies on plates uses bit of liquid to move and colonues plate, edge is where swarming typically happens
- cells are unattached and motile, metabolically active
how is swarming and biofilms different
biofilms = mass of metabolically quiescent cells attached firmly to a surface
advantages of swarming
- colonise new niches faster, nutrients shared within group so better survival
