Lecture 2: Bacterial Morphology and Structure 2 Flashcards
What is the glycocalyx of a bacterial cell
Polysaccharide containing material lying outside the cell wall
What are the two forms of glycocalyx
- Slime layer
- Capsule
What is the function of the glycocalyx
Promotes adherence, protects against desiccation, barrier to antibiotics, inhibits phagocytosis, virulence factor
T or F: some bacteria species are A-virulent if capsule is absent
True
What is a slime layer
Easily removed, diffuse, unorganized layer of extracellular material that surrounds bacterial cells
What are the functions of a slime layer
Protect the bacteria cells from environmental dangers like antibiotics and desiccation, adherence, permit to survive chemical sterilization
Is the following a slime layer or capsule
slime layer
What is a capsule
Well organized, uniform, rigid layer outside of cell wall
What is the Quellung Reaction
Test used to determine of bacteria has a capsule or not. Add anti-capsular antibodies, antigen-antibody reaction causes change in capsule so that is appears swollen and more visible
Is the following a capsule or slime layer
capsule
What is the gold standard for stereotyping pneumococcus
Quellung reaction
What are flagella
Fliamentous appendages composed entirely of proteins
What are the three major components of flagella
- Filament
- Hook
- Basal body
What is the function of flagella hooks
Attaches filament to the basal body
What is the function of the basal body of flagella
Anchors flagellum in the cell wall/membrane
Each flagellum is made up of several ___, composed of flagellum- ___ antigens
Protofilaments, H antigens
Why are identifying H antigens useful
Can help dx the type of bacteria
How many flagella in atrichous
None
How many flagella in lophotrichous
Multiple polar flagella- one one side
What does amphitrichous mean
Single flagellum or multiple flagella on both polar ends
What does peritrichous mean
Multiple flagella all over cell
Identify type of flagella 1-4
- Monotrichous
- Lophotrichous
- Amphitrichous
- Peritrichous
What are pili/fimbriae
Rigid, hair like proteinaceous structures
What is the function of pili/fimbriae
Attachment
What are the two main classes of pili
- Ordinary/common
- Sex/conjugation/ F pilus
What type of arrangement do ordinary/common pili have
Peritrichous
What is the purpose of the ordinary/common pili
Serve as virulence factors- adhere to host cells
What is the purpose of the sex/conjugation/F pili
Structure for conjugation, genetic exchange mechanism
What type of bacteria are sex/conjugation/F pilus found in
Gram negative bacteria
Where do prokaryotes package their DNA
Nucleoid
T or F: nucleoid lacks a nuclear membrane
True
What is the advantage of lacking a nuclear membrane
Allows for coupled transcription-translation
What are the advantages of coupled transcription-translation
Protein synthesis is faster, quicker response to environment (a reason for bacterial resistance)
Describe chromosome of bacterial
Single, circular chromosome, no introns in DNA no histones
What is the benefit of no introns and no histones in chromosomes
Allows for quick response to environment
What do plasmids code for
Non-essential information: includes genes that encode for:
1. Antibiotic resistance
2. Heavy metal resistance
3. Toxins
4. Useful metabolic enzymes
How can bacteria acquire plasmids
Various genetic exchange mechanisms
What are the bacterial ribosome subunits
70S: 50S and 30S
What is the purpose of ribosomes
Site for protein synthesis- coupled transcription-translation
What are inclusion bodies
Various granules, vesicles, and vacuoles within cytoplasm
How can inclusion bodies be helpful clincially
Can help in identification of some bacteria
What is an endospore
Resting stage that allows organism to survive harsh environmental conditions
Endospore formation is triggered by ___, such as ___
Unfavorable conditions, such as nutrient depletion
When a favorable condition returns an endospore will undergo __
Germination
What is the core of the endospore
Contains complete chromosome, protein synthesizing apparatus and energy generating system based on glycolysis
What is the spore wall
Innermost layer surrounding inner spore membrane, contains normal peptidoglycan and becomes the cell wall of the germinating vegetative state
What is the cortex of endospore
Thickest layer of the spore envelope. Cortex peptidoglycan extremely sensitive to lysozyme and autolysis plays a role in spore germination
What is the coat of an endospore
Composed of keratin like protein containing many intramolecular disulfide bonds. Impeccability of this layer is important for bacterial resistance
What is the exosporium
Composed of proteins, lipids, and carbohydrates
What is the difference between sporulation and vegetative growth
Sporulation: DNA replicates , eventually spore coat and spore form—> will germinate until an unfavorable condition occurs then will enter vegetative growth. Once favorable conditions return it will produce 2 new daughter cells
What are the two clinically relevant genera that produce endospores
Bacillus and clostridium
Are the genera that produce endospores gram positive or negative
Positive
What is the staining technique for detecting endospores
- Apply malachite green-primary stain
- Heat
- Water/decolarizer
4 apply safranin- counter stain
How do aminoglycosides serve as antibiotic
Bind 30S ribosomes causing misreading of genetic code
What are some examples of aminoglycosides
Gentamicin, tobramycin, amikacin, streptomycin, kanamycin
How do tetrcyclines work as antibiotics
Binds 30S ribosomes reversibly, prevents addition of amino acids to elongating peptide chain
How do lincosamides work as antibiotics
Binds to 50S ribosomes, inhibit peptidyl transferase
What are some examples of lincosamides
Linomycin, clindamycin, pirlimycin
How does chloramphenicol work as antibiotic
Binds 50S ribosomes inhibits peptidyl transferase
