L12 Bacterial Cell Structure and Function Flashcards
What are the 5 major cellular structures of a bacterium?
- Capsule
- Flagellum
- Pili
- Nucleoid
- Ribosomes
What are three other names for the capsule?
Mucoid layer, slime layer, glycocalyx
What are capsules made of?
Combination of polysaccharide, protein, and/or DNA
What are the two major functions of the capsule?
- Adherence
2. Immune system avoidance
What are organized multicellular bacterial communities?
Biofilms
What is the real reason antibiotics are resisted by bacteria in a biofilm?
The cells inside the biofilm differentiate and activate antibiotic resistant mechanisms.
When do biofilms form?
When bacteria sense the correct density of their cohort.
Cell-cel communication via ___ causes matrix synthesis, leading to the biofilm.
Pheromones
What are the major characteristics of a biofilm?
Adherence, controlled release of bacteria, immune system avoidance, alteration of bacterial growth kinetics, activation of bacterial stress and defense responses, alteration of drug PK
What is a potential strategy used to defeat biofilms?
Treat the biofilm (block pheromone communication), then treat the bacterium
The microbiota are likely present in ___ throughout the GI tract.
Biofilms
In humans, biofilms are most prominent in the ___ and ___. They decline toward the ___.
Proximal colon; appendix; distal colon
What is one possible mechanism for varying biofilm levels in the human GI tract?
IgA may act more profoundly in the distal colon, causing aggregation and removal of material via the flow of the GI tract.
What are the three types of flagellar organization?
- Monotrichous
- Lophotrichous
- Peritrichous
The immunological response to flagella can be a diagnostic tool - what is this called?
Serotyping
Flagella have a cap at the tip; how can this be advantageous?
Some bacteria replace the cap with an adhesion, allowing the flagella to stick to the host cell surface
Although pili and the capsule are critical mediators of attachment, many other surface molecules exist that can mediate this process; these are called ___.
Adhesins
Describe the gram negative cell envelope.
Inner and outer membranes, thin layer of peptidoglycan between the membranes, LPS in outer membrane
Describe the gram positive cell envelope.
Inner membrane only, peptidoglycan layer (thicker), teichoic acid and lipeteichoic acid
What is peptidoglycan?
A series of sheets stacked on top of each other; composed of glycan monomers linked together and then linked to adjacent strands with peptides.
What degrades peptidoglycan?
Lysozyme
What is the role of LPS?
Makes the outer membrane relatively impermeable compared to other memranes; porins are portal molecules used for transport in light of this
What are the three components of LPS?
- Lipid A
- Core
- O-specific side chain
What is Lipid A?
Part of LPS, sits in membrane, toxic, key inflammatory molecule
What is O-specific side chain?
Part of LPS, sugar polymer with lots of variation that can give some diagnostic utility
Describe the multidrug efflux system.
Allows for rapid transport of drugs out of the bacterium from the para- or cytoplasms.
Describe the process of sporulation in bacteria.
The normal division of the cell in half is done unequally in such a way that the smaller compartment pinches off inside the cell, forming a free protoplast. This morphs into a dormant, resistant, and metabolically inactive cell. The cell lyses and releases the spore
Describe the process of germination of a spore.
The spore sheds its protective structures and converts back into an active cell that is metabolically active and produces virulence factors.
What are mycoplasma?
Simple type of bacterium that is gram positive but lacks peptidoglycan outer membrane; however, it does have a complex polysaccharide layer with hydrophobicity and porins
