L28- introduction to microbiology and bacterial cells

what are the two types of cellular organisms

• eukaryote ( includes fungi/yeast and protozoa)

• prokaryote ( includes bacteria and archaea )

what are prions

its described as a piece of infectious protein with no nucleic acids. it can cause human proteins to change causing problems

e.g. BSE/ mad cow disease

what are the main differences between prokaryotes and eukaryotes

prokaryotes

• smaller ( 1-5 micrometres )

• they are haploid

• asexual reproduction

• unicellular

• no true nucleus

• cell wall

eukaryotes

• bigger ( >10 micrometres )

• diploid ( but not always )

• sexual reproduction ( but not always )

• unicellular/ multicellular

• true nucleus

what are key features/ characteristics of bacteria

• unicellular

• huge diversity in shape, size, habitat and metabolism

• mostly harmless

• some can cause diseases ( pathogenic )

• or pharmaceutical contaminants

• they are named using genus and species

why are microbes unwanted inside drugs

• they can cause infections

• they can affect the efficacy of the drug

what are the main ways of classifying bacteria

• morphology ( simplest way )

cell shape, size motility , spore forming

• metabolism

use of energy sources/nutrients

• molecular characteristics

protein, lipid structure, sequence of gene encoding

describe

• sequence a persons DNA with contamination for example and compare against a database

• it will tell you right down to the species

• very specific but requires a lot of equipment

why was it decided that it was the 16s ribosomal RNA gene that would be used for classiying bacteria

• all bacteria will have them

• the 16s gene is highly conserved ( it is similar in lots of different bacteria ) but contains hypervariable regions/ short sections of DNA that are different

• the variation is bigger in different species

structure of bacteria

briefly describe the structure of the plasma membrane on bacteria

• its made up of a selectively permeable phospholipid bilayer

• within the bilayer there are peripheral and integral proteins which medicate transport into and out of the cell and is typically the site of secretion and respiration as the bacteria don’t have mitochondria

• they are environmental regulators as the respond to what’s happening outside the cell like increasing salt levels

how does respiration occur in bacteria

as the bacteria don’t have mitochondria it occurs in a series of enzyme in the proteins across the cell membrane

explain the structures inside the cytoplasm and their functions

• ribosomes- 30s and 50s, 70s in total

• inclusion bodies- act as storage bodies as they store nutrients

• the cytoplasm also contains a high concentration of dissolved solute

explain the structure and the function of a nucleoid

• it is the genetic structure of bacteria/ bacterial chromosome

• its a double stranded DNA ( dsDNA ) that is supercoiled

• not enclosed by a membrane

• it contains one copy of a gene-haploid

what is the function of the plasmid

• they are extrachromosomal DNA, they are small circular dsDNA

• they replicate independently of chromosomes

• they encode auxiliary functions - contain gene that aren’t essential for survival but provide the organism with an advantage e.g. antibiotic advantage

what is thestructure and the function of the bacterial cell wall

• it protects the structure and provides rigidity and strength by preventing lysing

• makes an excellent drug target as its structure is unique to bacteria

• its composed of peptidoglycan that’s cross linked to form a mesh- a backbone made up of sugar residue bonded by glycosidic bonds but the crosslinking comes from the link between peptides on adjacent glycan backbones

• its important as it help it remain strong but due to it being mesh it still allows molecules inside and out

what are the two different types of pathogenic bacteria

gram positive

• stains purple

• has a thick peptidoglycan layer

• within the peptidoglycan layer there are teichoic acids and lipoteichoic acids

• e.g. staphylococcus aureus

gram negative

• stains pink

• has a thin layer of peptidoglycan

• its surrounded by a lipopolysaccharide outer membrane too

• in-between the lipopolysaccharides there are porins which are water filled channels

• e.g. E.coli

what are the features of lipopolysaccharides ( endotoxin )

• they are very immunogenic- triggers an immune response in the body

• toxic to animal cells

• heat resistant

what are some pathogenic bacteria that arent classified by gram staining

• acid- fast bacilli

they have an extra thick waxy layer

• atypical bacteria

bacteria that don’t have a peptidoglycan layer, they often cause intracellular infections

what are three examples of bacterial cell componets only present in some bacteria

• endospores

• capsules and slime layers

• pili and fimbriae

what is a bacterial endospore

they are also resistant to uv radiation, freezing high temps and most disinfection

difficult to kill due to being metabolically inactive

e.g C.diff which causes hospital associated diarrhoea

describe capsules and slimlayers

e.g streptococus pneumonia which causes pneumonia

describe what the fimbriae is and fili