Bacterial gnetics, metabolism and structure Flashcards
What is the primary role of nucleic acids in cells?
To encode hereditary information and play a role in the synthesis of proteins.
What are the two major classes of nucleic acids?
DNA (Deoxyribonucleic Acid) and RNA (Ribonucleic Acid).
How is the genetic material organized in prokaryotes?
It is not enclosed in a nucleus; instead, it is located in the cytoplasm and typically organized in a single circular chromosome.
Do prokaryotes have a nuclear membrane?
No, prokaryotes do not have a nuclear membrane.
How do prokaryotes divide?
Through binary fission.
How many chromosomes do prokaryotes typically have?
One circular chromosome.
What is the size of ribosomes in prokaryotes?
70S.
How is the genetic material organized in eukaryotes?
It is enclosed within a nuclear envelope and organized into linear chromosomes associated with histones.
How many chromosomes do eukaryotes typically have?
More than one chromosome.
What is the size of ribosomes in eukaryotes?
80S
Prokaryotes vs. Eukaryotes
DNA within a nuclear membrane - X
Membrane Bound Organelles - X
Prokaryotes
Prokaryotes vs. Eukaryotes
Cell wall containing peptidoglycan - /
Eukaryotes
a double-stranded, closed, circular DNA molecule that exists independently of the bacterial chromosome.
plasmid
How do plasmids replicate?
Plasmids replicate autonomously, independently of the bacterial chromosome.
How many plasmids can be present in a bacterial cell?
The number of plasmids per cell can vary.
What kind of genes do plasmids contain?
Plasmids contain several genes, which can include those for antibiotic resistance, virulence factors, or other functions.
What are transposable elements also known as?
“Jumping genes.”
How do transposable elements move within the genome?
They move from one genetic element to another, such as between plasmids and chromosomes.
Can transposable elements replicate independently?
No, they cannot replicate independently and require a host genome for replication.
What are the two types of transposable elements?
Simple transposon (insertion sequence or IS) and composite transposon.
what type of transposable element contains only the genes necessary for its movement and insertion.
simple transposon (IS)
what type of transposable element contains additional genes, such as those for antibiotic resistance, flanked by IS elements.
composite transposon
a plasmid capable of replicating independently of the host chromosome and is considered part of the bacterial genome.
episomes
How does the stability of episomes compare to chromosomal DNA?
Episomes are not as stable as chromosomal DNA and may be lost during cell replication.
the process by which a single bacterial cell divides to produce two genetically identical daughter cells.
binary fission
Why must the genome be replicated during cell division?
To ensure that each daughter cell receives an identical copy of the functional DNA.
What is the purpose of DNA replication being accurate?
To prevent mutations and ensure the genetic information is correctly passed on to daughter cells.
Genetic exchange: the uptake of naked (free) DNA from the environment by a bacterial cell.
Transformation
How does DNA enter a recipient cell during transformation?
DNA is released into the environment when a donor bacterial cell dies and undergoes lysis
Which bacteria are known to undergo transformation?
Haemophilus, Streptococcus, and Neisseria.
What types of traits can transformation confer to bacteria?
Antibiotic resistance and the ability to cause disease.
Is transformation limited to bacteria of the same species?
No, transformation can occur between bacteria of different species.
Genetic exchange: transfer of bacterial DNA from one bacterium to another via a bacteriophage.
transduction
Transduction is the transfer of bacterial DNA from one bacterium to another via
bacteriophage
What types of transduction are there?
Generalized transduction and specialized transduction.
Type of transduction: Any bacterial DNA can be transferred when a bacteriophage mistakenly packages bacterial DNA into its viral capsid.
generalized transduction
type of transduction: Specific bacterial genes are transferred when a bacteriophage integrates into the bacterial genome and excises incorrectly, carrying adjacent bacterial genes.
specialized transduction
Genetic exchange: the transfer of genetic material between two living bacterial cells through direct cell-to-cell contact.
COnjugation
How is conjugation mediated in bacteria like E. coli?
By a sex pilus, a protein appendage that facilitates contact between donor and recipient cells.
What role do plasmids play in conjugation?
Plasmids are transferred from the donor cell to the recipient cell and must be replicated.
genetic elements that can move from one location to another within the genome, facilitating genetic recombination.
Transposons
What is the primary purpose of metabolic pathways in bacteria?
The acquisition of nutrients from the environment.
What molecules can pass through bacterial cell membranes via simple diffusion?
Water, oxygen, and carbon dioxide.
What is the most common method for the uptake of nutrients in bacteria?
Active transport.
Acquisition of nutrient:
A transport mechanism that requires energy and involves the chemical modification of the transported substance during its passage through the cell membrane.
group translocation
Methods of Nutrient Acquisition: Energy-dependent transport of nutrients
Active transport
What is the Embden-Meyerhof-Parnas (EMP) pathway more commonly known as?
Glycolysis
Name an alternative pathway to glycolysis for the degradation of gluconate and glucose.
The Entner-Doudoroff pathway.
What cycle follows glycolysis in bacterial metabolism?
The Tricarboxylic Acid (TCA) cycle, also known as the Krebs cycle.
what are the 2 alternate pathways for the production of metaolites
- Entner-Doudoroff pathway
- Pentose Phosphate pathway
Why is energy production important for bacteria?
It produces the energy required for nearly all cellular processes, including nutrient uptake and precursor production.
What are the two main types of phosphorylation that generate ATP in bacteria?
Substrate-level phosphorylation and oxidative phosphorylation.
What is the terminal electron acceptor in aerobic respiration?
oxygen
What are some possible terminal electron acceptors in anaerobic respiration?
Nitrate, sulfate, and other molecules other than oxygen.
Main purpose is To produce essential building blocks such as amino acids, fatty acids, sugars, and nucleotides from precursor products.
Biosynthesis
What type of metabolism is biosynthesis dependent on?
Anabolic metabolism.
The process of assembling smaller building blocks into larger macromolecules.
Polymerization and Assembly
What drives the synthesis of macromolecules in bacterial cells?
The synthesis is driven by energy (often in the form of ATP) and enzymatic activity.
5 macromolecules
lipids
lipopolysaccharides
polysaccharides
proteins
nucleic acids
What type of microorganisms are bacteria?
Single-cell prokaryotic microorganisms.
Do bacteria have membrane-bound organelles?
No, bacteria lack membrane-bound organelles.
How do bacteria typically reproduce?
By binary fission.
Are fungi and parasites prokaryotic or eukaryotic?
They are eukaryotic.
Can fungi be single-cell or multicellular?
Yes, fungi can be single-cell (yeasts) or multicellular (molds).
Are viruses considered cellular organisms?
No, viruses are not considered cellular organisms.
Why do viruses need a host cell?
They need a host cell to replicate because they cannot reproduce independently.
abnormal infectious proteins.
Prions
Do prions contain genetic material?
No, prions do not contain DNA or RNA.
Bacterial morphology: circular/spherical
cocci
Bacterial morphology: Ovoid/slightly elongated
coccobacilli
Bacterial morphology: Rod shaped
bacilli
Bacterial morphology: Rod-shaped with pointed ends
Fusiform
Bacterial morphology:
curved / comma like
curved
Bacterial morphology: spiral / helical
spiral
What color do gram-positive bacteria stain?
Deep blue or purple
What color do gram-negative bacteria stain?
Pink to red
What is the main structural difference between gram-positive and gram-negative bacteria?
Gram-positive bacteria have a thick peptidoglycan layer, while gram-negative bacteria have a thin peptidoglycan layer and an outer membrane.
what are the steps for staining
Primary stain
Mordant
Decolorizer
Counterstain
What is the first step in preparing a bacterial sample for Gram staining?
Prepare a smear of the bacterial sample on a microscope slide, air dry it, and then heat-fix the cells to the slide.
What is the primary stain used in Gram staining?
Crystal violet.
It acts as a mordant, forming a complex with the crystal violet that gets trapped in the thick peptidoglycan layer of gram-positive cells.
Grams Iodine
Gram staining decolorizer
Alcohol or acetone
What is the role of the decolorizer in Gram staining?
The decolorizer (alcohol and/or acetone) removes the crystal violet-iodine complex from gram-negative cells but not from gram-positive cells, due to differences in cell wall structure.
What is the counterstain used in Gram staining, and what is its purpose?
Safranin is the counterstain used to stain gram-negative cells pink to red, providing a contrast to the deep blue or purple of gram-positive cells.
Who developed the Gram stain technique?
Hans Christian Gram.
What is the primary purpose of the Gram stain?
To provide a rapid, presumptive identification of microorganisms.
Why is the Gram stain considered a differential stain?
Because it differentiates bacteria based on their cell wall structure, allowing for the distinction between gram-positive and gram-negative bacteria.
Why do gram-positive bacteria retain the crystal violet dye?
Because they have a thick peptidoglycan layer that traps the crystal violet-iodine complex.
Why do gram-negative bacteria allow the crystal violet to wash out easily?
Because they have a thin peptidoglycan layer and an outer membrane, which does not retain the crystal violet-iodine complex when decolorized.
What type of cell wall do gram-positive bacteria have?
A thick peptidoglycan layer with numerous teichoic acid cross-linkages.
What additional structure do gram-negative bacteria have that gram-positive bacteria do not?
An outer lipid bilayer.
what staining technique, identify bacteria whose cell walls contain long-chain fatty acids, such as mycolic acid.
acid-fast stain
Why is the acid-fast stain considered a differential stain?
Because it distinguishes bacteria based on their cell wall composition, specifically the presence of mycolic acids.
What makes acid-fast bacteria resistant to decolorization by acid alcohol?
The presence of long-chain fatty acids (mycolic acids) in their cell walls.
Which genus of bacteria is most commonly associated with being acid-fast?
Mycobacterium
What is the primary stain used in acid-fast staining?
Carbolfuchsin red.
What solution is used as the decolorizer in acid-fast staining?
An acid alcohol solution, typically a mixture of hydrochloric acid and ethanol.
What happens to non-acid-fast cells during the decolorization step in acid-fast staining?
They lose the carbolfuchsin red stain and become colorless.
What is the counterstain used in acid-fast staining?
Methylene blue.
What color do acid-fast bacteria appear after acid-fast staining?
red
What color do non-acid-fast bacteria appear after acid-fast staining?
blue
What are the two main divisions of bacterial cell components?
Outer cell structure and its appendages (cell envelope), and the cell’s interior.
What type of bacteria have an outer membrane as part of their cell envelope?
Gram-negative bacteria.
What is the primary component of the bacterial cell wall?
Peptidoglycan macromolecules (murein layer).
What is the function of the cytoplasmic or cell membrane?
It encloses the cytoplasm, regulates the entry and exit of substances, and is involved in various metabolic processes.
protein structures located in the outer membrane that form water-filled channels controlling the passage of nutrients and solutes (including antibiotics).
Porins
They facilitate the attachment of the outer membrane to the cell wall and serve as adhesins for attachment to a host cell or as transporters.
Murein lipoproteins
It is the space between the outer membrane and the cytoplasmic membrane, found in gram-negative bacteria
Periplasm
outer membrane is composed of
lipopolysaccharides
It contains essential enzymes and proteins, plays a role in disease causation, and houses porins for nutrient and solute passage.
Outer membrane
What is the main component of the bacterial cell wall?
Peptidoglycan (murein) layer.
Provides shape and strength to the cell, protects against mechanical disruption, and acts as a barrier to larger substances.
Cell wall
What two molecules make up the disaccharide-pentapeptide units in the peptidoglycan layer?
- N-acetylglucosamine (NAG)
- N-acetylmuramic acid (NAM).
In which type of bacteria is the peptidoglycan layer thicker?
Gram-positive bacteria.
What are teichoic acids composed of?
Glycerol or ribitol phosphate polymers combined with various sugars, amino acids, and amino sugars.
In which type of bacteria are teichoic acids found?
Gram-positive bacteria.
How are teichoic acids linked within the bacterial cell?
They can be linked to N-acetylmuramic acid or to the cytoplasmic membrane as lipoteichoic acid
In which bacteria are mycolic acids found?
Mycobacteria.
What is the function of mycolic acids in bacterial cells?
They make the cell more refractory to toxic substances, such as acids.
In which type of bacteria is the periplasmic space typically found?
Gram-negative bacteria
What structures bound the periplasmic space?
The internal surface of the outer membrane and the external surface of the cytoplasmic membrane.
What layer is contained within the periplasmic space?
The murein (peptidoglycan) layer.
What is the function of the gel-like substances in the periplasmic space?
They assist in capturing nutrients from the environment.
Periplasmic space component that assist in capturing nutrients from the environment.
Gel like substances
What types of enzymes are found in the periplasmic space?
Enzymes involved in the degradation of macromolecules and detoxification of environmental solutes, such as antibiotics.
In which type of bacteria is the Cytoplasmic (inner) membrane typically found?
both gram positive and negative
Where is the cytoplasmic membrane located within the bacterial cell?
It is the deepest layer of the cell envelope.
What components are heavily present in the cytoplasmic membrane?
Various proteins and enzymes vital to cellular metabolism.
What additional function does the cytoplasmic membrane serve besides housing metabolic proteins and enzymes?
It acts as an additional osmotic barrier.
Where is the capsule located in gram-positive bacteria?
Exterior to the murein layer.
Where is the capsule located in gram-negative bacteria?
Exterior to the outer membrane.
What is the capsule composed of?
High molecular weight polysaccharides.
Its function is it Protects the bacteria from attack by the human immune system and facilitates bacterial colonization on surfaces.
Bacterial capsule
What are fimbriae or pili composed of?
Proteinaceous structures.
Hairlike, Proteinaceous structures.
Fimbriae or pili
What is the function of fimbriae or pili?
Serve as adhesins to help bacteria attach to host cell surfaces.
What specific function does the sex pilus serve in E. coli?
Acts as a conduit for the passage of DNA during conjugation.
What protein composes flagella?
Flagellin.
What is the primary function of flagella?
Bacterial motility.
What type of flagellation involves flagella at both ends of the bacterial cell?
Lophotrichous.
What type of flagellation involves a single flagellum at one end of the bacterial cell?
Monotrichous.
What type of flagellation involves a single flagellum at both ends of the bacterial cell?
Amphitrichous
What type of flagellation involves flagella covering the entire cell surface?
Peritrichous.
cell interior is composed of?
- cytosol
- nucleoid
- plasmids
4, endospores
What main functions occur in the cytosol of bacterial cells?
Nearly all cellular functions not conducted by the cell membrane, including metabolic processes and protein synthesis.
Why does the cytosol have a granular appearance?
Due to the presence of polysomes and inclusions such as storage granules.
What is the storage form of glucose in bacterial cells?
Glycogen.
What is the storage form of inorganic phosphates in bacterial cells?
polyphosphate granules
Highly coiled DNA intermixed with RNA, polyamines, and various proteins.
Nucleoid
Extrachromosomal genetic elements that exist independently in the cytosol.
plasmids
Highly resistant, dormant structures formed by some bacteria.
endospores
