Bacterial Structure And Classification Flashcards
What are the types of prokaryotes?
Archaea and bacteria
What is the k antigen in bacteria?
Codes for the capsule which shields bacteria from host self-defence mechanisms.
What is the O antigen in bacteria?
It is the outermost surface lipopolysaccharide present in the cell walls of -ve bacteria, which is highly variable
What is the H antigen in bacteria?
Threadlike portion of the flagella of bacteria.
What is the role of pilli in bacteria?
Create fimbraie for adhesion.
What is a +ve bacteria?
Gram positive Bacteria with a peptidoglycan cell wall and surface teichoic acid which stabilises the structure.
What is a -ve bacteria?
Gram negative bacteria with an outer lipopolysaccharide membrane that uniquely contains the O-antigen on surface LPS. It has a gel matrix called the periplasm and an inner peptidoglycan cytoplasmic membrane.
How can +ve and -ve bacteria be differentiated?
Use of crystal violet stain, which is retained in Gram +ve bacteria.
It is washed out in Gram -ve bacteria and causes it to turn pink.
What is acid fast bacteria?
Bacteria such as mycobacterium tuberculosis which have a highly waxy and impermeable cell wall to disinfectants and stain due to the presence of mycolic acid. Therefore, it requires the use of fuschin stain to make it pink to view the structure.
What is lactose used for by bacteria?
Lactose is broken down -> glucose + galactose -> lactic acid as a carbon source, which lowers the pH of surroundings.
How can we differentiate between lactose-using bacteria?
MacConkey agar medium that is
Selective only for -ve bacteria due to presence of crystal violet and bile salts which inhibit +ve growth.
Differential for lactose-fermenting bacteria.
How does MacConkey agar show the differential for lactose fermenting bacteria?
Drop in pH due to lactic acid presence causes solution to turn pink. E.Coli is a lactose-fermenting -ve bacteria.
What is a chromosome nucleoid?
Consists of a chromosome and plasmid, in bacteria.
What is a plasmid?
Small, circular double stranded DNA molecule that replicate independently outside the chromosome in bacteria.
What is transformation?
Bacteria take up genetic material from the environment.
