QVprep Microbiology Lessons

Bacterial Anatomy

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Prokaryote: While bacteria and archaea are classified in separate domains, neither have a membrane bound nucleus, which is the definition of a prokaryote. The term prokaryote is used to denote a cell that does not have a nucleus, as in bacteria and archaea.


Peptidoglycan: The purpose of peptidoglycan in bacteria is cell wall composition. Peptidoglycan is a complex carbohydrate that is the primary structural component in the cell wall.


Periplasm: The periplasm or periplasmic space is the region between the outer membrane or LPS in Gram negative bacteria and the plasma membrane. It consists of a fluid (gel) filled space in which peptidoglycan resides.


Bacterial cell wall: The cell wall is the basis for the classification of bacteria as gram-positive or gram-negative. Techoic and lipotechoic acids molecules are a constituent of gram positive cell walls but are not found in gram negative cell walls. Just like LPS is found only in gram-negative bacteria, techoic acids are only a part of the composition of gram-positive cell walls. The cell wall will retain the stains introduced during the Gram stain as a result of varying degrees of thickness and composition, as demonstrated by gram-negative and gram-positive bacteria. The cell wall of the bacterial cell is characterized by cross linking of N-acetyl glucosamine (NAG) and N-acetylmuramic acid. Peptidoglycan is characterized by NAG-NAM cross linking and this makes up the bacterial cell wall.