What are the three basic shapes of bacterial cells?
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Cocci, bacilli, and spirilla.
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What are the three basic shapes of bacterial cells?
Cocci, bacilli, and spirilla.
How do bacteria obtain nutrients?
By taking up small molecules across the cell wall.
What are flagella in bacteria?
Long helical filaments extending from the cell surface that enable movement.
What is an additional structure that may be found external to the cell wall?
A capsule of high molecular weight polysaccharides or amino acids.
Why is accurate replication of DNA essential?
Because DNA carries the information that defines the properties and processes of a cell.
What shape do cocci bacteria have?
Spherical.
What types of small molecules do bacteria take up?
Amino acids, oligosaccharides, and small peptides.
How do bacterial flagella differ from eukaryote flagella?
Bacterial flagella do not utilize adenosine triphosphate (ATP) for movement.
How does DNA polymerase ensure accurate replication?
By proofreading newly incorporated deoxyribonucleotides and excising incorrect ones.
What methods are used for the classification of bacteria?
A mixture of microscopic, macroscopic, and biochemical characteristics.
What is the function of the capsule in bacteria?
It provides protection against phagocytosis and is important for virulence.
What shape do bacilli bacteria have?
Rod-shaped.
What does CFU stand for in microbiology?
Colony-forming units.
What are flagella primarily made of?
Protein components called flagellins.
What is the frequency of errors in DNA replication?
Approximately one mistake per 10^10 nucleotides copied.
How can Gram-negative bacteria utilize larger molecules?
After preliminary digestion in the periplasmic space.
What are some characteristics used to classify bacteria?
Size, shape, color, staining properties, respiration, and reproduction.
What is the primary catabolic pathway for glucose breakdown?
Glycolysis.
What is the significance of capsulated organisms in Streptococcus pneumoniae infections?
Only a few capsulated organisms can cause a fatal infection, while unencapsulated mutants cause no disease.
What shape do spirilla bacteria have?
Spiral or corkscrew-shaped.
What is the significance of CFU in bacterial growth?
It is used to estimate the number of viable bacteria in a sample.
Why are flagellins significant in bacteria?
They are strongly antigenic and serve as H antigens, important for antibody responses.
What type of analysis is used for more sophisticated classification of bacteria?
Immunologic and molecular criteria.
What is the final hydrogen acceptor in aerobic respiration?
Oxygen.
What can cause different rates of transcriptional initiation in promoters?
Regulatory proteins can alter their activities.
What role does the cell wall play in bacteria?
It is a major contributor to the ultimate shape of the organism, important for bacterial identification.
What does a bacterial growth curve represent?
The growth of bacterial populations over time.
How do bacteria adapt to changes in their environment?
By controlling gene expression to ensure proteins are produced only when needed.
What happens to glucose in anaerobic conditions?
It undergoes fermentation, with other molecules acting as final hydrogen acceptors.
What role does the sigma factor play in transcription?
It is important for promoter recognition.
What can the easily determined characteristics of bacteria be used for?
To divide organisms into conventional taxonomic groupings.
What are the main phases of the bacterial growth curve?
Lag phase, log phase, stationary phase, and death phase.
How are bacterial shapes generally categorized?
As spherical (cocci), rods (bacilli), or helical (spirilla), with variations.
What type of organisms are bacteria?
Single-celled prokaryotes.
Why is the regulation of virulence determinants important for pathogenic bacteria?
It conserves metabolic energy and ensures production only when needed.
What are bacterial genes present on?
DNA as separate discrete units (single genes) or as operons (multigenes).
What are the different groups of organisms that can cause infectious diseases?
Prions, viruses, bacteria, fungi, protozoa, helminths (worms), and arthropods.
What are some examples of detoxifying enzymes that interact with harmful compounds?
Superoxide dismutase, peroxidase, and catalase.
How can bacteria switch on sets of genes?
By altering the level of expression of a particular sigma factor.
What are some common final hydrogen acceptors in fermentation?
Lactic acid, ethanol, and carbon dioxide.
Which group of bacteria is mentioned in the context of classification?
Gram-positive bacteria.
How is bacterial DNA structured?
It forms a long circular molecule, not contained within a defined nucleus.
What environmental change occurs when enterobacterial pathogens enter the human gut?
Temperature rises to 37 °C, with abundant carbon and nitrogen, and low oxygen and free iron availability.
What specifies the exact sequence of amino acids in a protein?
The sequence of nucleotides found in the mRNA transcripts.
What type of properties does the outer membrane of Gram-negative bacteria have?
Hydrophilic and hydrophobic properties due to lipid components.
What type of mRNA is produced from single genes?
Monocistronic mRNA.
Why is correct identification of infectious organisms important?
It is essential for accurate diagnosis and effective treatment.
How do cells uptake and transport nutrients into the cytoplasm?
Through the cell membrane using various transport mechanisms, including facilitated diffusion and active transport.
What is the role of detoxifying enzymes in bacteria?
To neutralize harmful compounds, particularly reactive oxygen species.
What is produced during the catabolic breakdown of glucose?
ATP, NADH, and pyruvate.
Why is the presence of different sigma factors important in bacteria?
It allows for the control of gene expression, such as in spore formation in Gram-positive bacteria.
What is a common method of bacterial reproduction?
Binary fission.
What happens to bacterial gene expression when they encounter a new environment?
They switch on or off a range of metabolic and virulence-associated genes.
How do hydrophilic molecules enter Gram-negative bacteria?
Through special channels or pores formed by proteins called 'porins'.
What is the process by which ribosomes and tRNA molecules produce a protein?
Translation.
What type of mRNA is produced from operons?
Polycistronic mRNA.
How are bacteria classified based on their cell wall?
As Gram-positive or Gram-negative.
What system is used for the classification of species in eukaryotes and some prokaryotes?
The binomial system of classification.
What is facilitated diffusion?
A transport mechanism that utilizes a carrier to move compounds to equalize their intra- and extracellular concentrations.
What harmful compounds do detoxifying enzymes interact with?
Reactive oxygen species and other harmful compounds.
What is the potential range of transcriptional initiation rates for different promoters?
Up to 3000-fold.
What is the most common way of altering gene expression?
By changing the amount of mRNA transcription.
Why is the correct identification of bacteria below the species level important?
To differentiate pathogenic and non-pathogenic forms.
What is the basic shape of a generalized bacterium?
Bacteria can have various shapes, including cocci (spherical), bacilli (rod-shaped), and spirilla (spiral).
What allows many bacteria to be motile?
A unique pattern of flagella.
What must a bacterial cell do before it can divide?
Duplicate its genomic DNA.
What is the significance of low nutrient levels in contaminated water for bacteria?
It triggers a change in gene expression when they enter a nutrient-rich environment.
What are the two properties conferred by lipopolysaccharide (LPS) in Gram-negative bacteria?
Antigenic properties (O antigens) and toxic properties (endotoxin from lipid A).
What is the role of promoters in bacterial gene expression?
They initiate the transcription of genes.
What does each set of three bases (triplet) in the mRNA sequence correspond to?
A codon for a specific amino acid.
What is a 'genus' in biological classification?
A group of closely related but non-interbreeding species.
What is the main structural component of the bacterial cell wall?
Peptidoglycan.
What is active transport?
A process where energy is expended to deliberately increase intracellular concentrations of a substrate.
What is the growth characteristic of obligate aerobes in the presence of oxygen?
Growth occurs.
How does superoxide dismutase function in detoxification?
It converts superoxide radicals into hydrogen peroxide.
How can the level of mRNA transcription be altered?
By changing the efficiency of binding of RNA polymerase to promoter sites.
What does gene expression involve?
Decoding genetic information to produce functional proteins or RNA molecules.
What type of organisms are bacteria classified as?
Prokaryotes.
What is the function of the bacterial cell wall?
It provides structural support and protection to the bacterium.
What begins the process of translation?
Formation of an initiation complex.
What surrounds the bacterial cell?
A complex cell wall and often a thick capsule.
What shape do all bacterial genomes have?
Circular.
What properties are used to identify important subspecies groups of some bacteria?
Immunologic properties.
What is unique about the peptidoglycan layer in Gram-positive mycobacteria?
It has a different chemical basis for cross-linking to the lipoprotein layer.
What happens to mRNA after it is transcribed?
It is translated into protein.
What is code degeneracy?
The redundancy in the triplet code resulting in more than one triplet encoding the same amino acid.
What factors largely influence bacterial growth and division?
The availability of nutrients.
How is each organism identified in the binomial system?
By two names indicating the 'genus' and the 'species'.
What are the two hexose sugars that make up peptidoglycan?
N-acetylglucosamine and N-acetylmuramic acid.
Where does oxidative metabolism occur in bacteria?
At the membrane-cytoplasm interface.
What enzymes are present in obligate aerobes?
Oxygen detoxifying enzymes such as superoxide dismutase, catalase, and peroxidase.
What is the function of catalase in bacteria?
It decomposes hydrogen peroxide into water and oxygen.
What mediates most instances of transcriptional regulation?
Regulatory proteins that bind to DNA adjacent to or overlapping the promoter site.
What enzyme is responsible for copying DNA during transcription?
DNA-dependent RNA polymerase.
What is the primary product of most gene transcription?
Messenger RNA (mRNA).
What is the role of the plasma membrane in bacteria?
It regulates the movement of substances in and out of the cell.
How is bacterial DNA different from eukaryotic DNA?
Bacterial DNA contains no introns.
What components make up the initiation complex?
mRNA, ribosome, and an initiator tRNA molecule carrying formylmethionine.
What types of metabolic patterns do bacteria exhibit?
Both aerobic and anaerobic.
What is the site where bacterial DNA replication begins called?
Origin of replication (OriC).
What types of antigens are used in tests with specific antisera?
Cell wall, flagellar, and capsule antigens.
What do mycolic acids in the outer envelope of mycobacteria create?
A waxy layer that alters staining properties and provides resistance to environmental factors.
How many codons encode all 20 amino acids, including start and stop signals?
A total of 64 codons.
How quickly can a single E. coli cell divide in rich laboratory media?
In as little as 20 minutes.
Give an example of an organism identified using the binomial system.
Homo sapiens and Escherichia coli.
How do microaerophiles grow in relation to oxygen levels?
They grow in low oxygen levels.
What are the nutritional requirements of E. coli?
E. coli can be grown in media providing only glucose and inorganic salts.
What are the regions of DNA where regulatory proteins bind called?
Operators or operator sites.
Describe the peptidoglycan layer in Gram-positive bacteria.
It forms a thick layer (20-80 nm) external to the cell membrane.
What is produced as a result of transcription?
An RNA transcript.
What percentage of genes in E. coli are transcribed into mRNA?
Up to 98%.
What is contained within the bacterial cytoplasm?
It contains ribosomes, genetic material (DNA), and various enzymes.
Where is bacterial DNA located within the cell?
In a region known as the 'nucleoid'.
What is the role of Shine-Dalgarno sequences in translation?
Ribosomes bind to specific sequences in mRNA to initiate translation.
What type of complex binds to the origin of replication to initiate DNA unwinding?
A multienzyme replication complex.
Which bacteria are examples where serogroups and serotypes are defined?
Salmonellae, streptococci, shigellae, E. coli.
What are acid-fast bacteria?
Bacteria with a waxy layer that alters their staining properties.
How are related genera classified?
They are grouped into progressively broader and more inclusive categories.
What is the division time for E. coli in a nutritionally depleted environment?
1 to 2 hours.
What is the growth characteristic of obligate anaerobes?
No growth in the presence of oxygen.
What type of media do Streptococci require for growth?
Complex media providing many organic compounds.
What data is used for the classification of bacteria?
Both phenotypic and genotypic data.
How thick is the peptidoglycan layer in Gram-negative bacteria?
It is thin (5-10 nm).
What are the two distinct classes of regulatory proteins?
Activators (increase transcription) and repressors (inhibit transcription).
What do ribonucleotides do during transcription?
They incorporate and base pair with the template DNA.
What types of RNA are produced from some genes besides mRNA?
Ribosomal RNA (rRNA) and transfer RNA (tRNA).
What is the purpose of bacterial pili?
They help in attachment to surfaces and in conjugation (gene transfer).
What are plasmids?
Small circular self-replicating DNA molecules that may carry extrachromosomal genetic information.
What is the START codon in translation?
AUG.
Which enzymes are involved in unwinding and separating DNA strands during replication?
Helicases and topoisomerases (e.g., DNA gyrase).
What can biochemical characteristics define in bacteria?
Other subspecies groupings such as biotypes, strains, and groups.
What activity do mycobacterial cell wall components promote?
Adjuvant activity, which promotes immunologic responsiveness.
Do all bacteria have the same nutritional requirements for growth?
All bacteria have similar general nutritional requirements for growth.
How often does Mycobacterium tuberculosis divide?
Every 24 hours.
What is the growth characteristic of facultative anaerobes/aerobes?
Growth occurs in both the presence and absence of oxygen.
What do genes subject to negative regulation bind?
Repressor proteins.
What is found in the outer membrane of Gram-negative bacteria?
Lipoproteins and lipopolysaccharides.
Which type of data is most valuable for clinical purposes?
Phenotypic data.
Where does transcription initiate?
At promoters.
What is the role of ribosomal RNA?
It provides a scaffold for assembling ribosomal subunits.
What is the function of flagella in bacteria?
They provide motility, allowing bacteria to move towards or away from stimuli.
What organelles are present in the cytoplasm of bacteria?
Only ribosomes for protein synthesis.
How does the polypeptide chain elongate during translation?
Through the movement of the ribosome along the mRNA and recruitment of further tRNA molecules.
What serves as a template for DNA polymerase during replication?
The separated DNA strands.
What does certain strains of Staphylococcus aureus release that affects red blood cells?
β-haemolysin.
What type of nutrition do all pathogenic bacteria exhibit?
Heterotrophic.
What is the initial phase of bacterial growth when introduced to a new environment?
Lag phase.
What is the relationship between bacterial growth and reactive oxygen species?
Bacteria's ability to grow in oxygen relates to their ability to enzymatically deal with potentially destructive reactive oxygen species.
What enzyme can digest the bacterial cell wall?
Lysozyme.
What is essential for understanding phenotypic data?
An understanding of bacterial structure and biology.
What do genes subject to positive regulation need to bind?
Activated regulatory protein(s) to promote transcription initiation.
What is the function of transfer RNA (tRNA)?
It participates in decoding mRNA into functional proteins.
What are promoters?
Nucleotide sequences in DNA that can bind RNA polymerase.
What is the difference in ribosome size between prokaryotes and eukaryotes?
Prokaryotic ribosomes are characterized as 70 S, while eukaryotic ribosomes are 80 S.
What is the genetic material of a bacterium?
It is typically a single circular strand of DNA.
What type of reaction do ribosomes carry out during translation?
A condensation reaction that couples incoming amino acids to the growing polypeptide chain.
What is incorporated during the polymerization reaction in DNA replication?
Deoxyribonucleotides.
How is antibiotic susceptibility useful in bacterial identification?
It helps in determining the identification of bacteria.
What is the term for mRNA transcripts that encode more than one protein in bacteria?
Polycistronic.
How do bacteria obtain energy?
By oxidizing preformed organic molecules (carbohydrates, lipids, and proteins) to yield ATP.
What occurs during the log or exponential phase of bacterial growth?
Cell division rapidly occurs, with the population doubling at a constant rate.
Which antibiotics disrupt the synthesis of peptidoglycan?
β-lactam and glycopeptides.
What factors can influence the frequency of transcription initiation?
The DNA sequence of the promoter site, DNA topology, and regulatory proteins.
What functions do prokaryotic cell membranes perform?
Many metabolic functions typically carried out by membrane-bound organelles in eukaryotes.
What is the significance of plasmids in bacteria?
Plasmids are small, circular DNA molecules that can carry genes for antibiotic resistance.
When does translation terminate?
When the ribosome encounters one of three termination codons: UGA, UAA, or UAG.
What forms during the DNA replication process?
Two characteristic replication forks.
What technique may be used to differentiate between isolates of Vibrio cholerae?
Phage typing.
What is a monocistronic arrangement in bacterial genes?
An arrangement with a single promoter, structural gene, and transcriptional terminator.
What are the two types of metabolism in bacteria?
Aerobic and anaerobic.
What happens during the stationary phase of bacterial growth?
Cell growth slows to a stop as nutrients are depleted and toxic products accumulate.
How does DNA topology affect transcription?
Supercoiling can influence the frequency of transcription initiation.
What surrounds the cell in all bacteria except mycoplasmas?
A complex cell wall.
What do the two copies of genetic information produced during replication consist of?
One parental strand and one newly synthesized strand of DNA.
What direct genetic approaches are used in bacterial identification?
Polymerase chain reaction (PCR) and probes to detect organism-specific sentinel DNA sequences.
What is an operon?
A polycistronic arrangement with a single promoter and terminator flanking multiple structural genes.
What is the major cellular role of Carbon in cells?
Molecular ‘building block’ obtained from organic compounds or CO2.
What is the final electron acceptor in aerobic metabolism?
Oxygen.
What is the final phase of bacterial growth after the stationary phase?
Decline (death) phase.
What role do regulatory proteins play in transcription?
They can bind adjacent to and may overlap the promoter site, influencing transcription initiation.
What external structures may be found outside the bacterial cell wall?
Capsules, flagella, and pili.
What is the significance of operon transcription?
It ensures that protein subunits required for enzyme complexes are synthesized simultaneously and in the correct stoichiometry.
What percentage of cell dry weight is Oxygen?
20%.
What can be the final electron acceptor in anaerobic metabolism?
An organic or inorganic molecule other than oxygen.
What is the role of Oxygen in aerobic respiration?
O2 is an electron acceptor.
Which operon encodes proteins for the uptake and metabolism of lactose?
The lac operon.
What does 'obligate' mean in the context of oxygen requirement for respiration?
It means the organism requires oxygen for respiration.
What is Nitrogen a component of?
Amino acids, nucleotides, nucleic acids, and coenzymes.
What pathogenic property is encoded by operons in Vibrio cholerae?
Cholera toxin.
What does 'facultative' mean regarding bacterial metabolism?
It refers to the ability to switch between aerobic and anaerobic metabolism.
How is Hydrogen involved in cellular processes?
It is a molecular ‘building block’ and is involved in respiration to produce energy.
What do fimbriae (pili) of uropathogenic E. coli mediate?
Colonization.
What is the basic shape of a generalized bacterium?
Bacteria can have various shapes, including cocci (spherical), bacilli (rod-shaped), and spirilla (spiral).
Why can anaerobic metabolism be used in the host's body?
Because appropriate substrates are usually available even in the absence of oxygen.
What cellular components is Phosphorus found in?
Nucleotides, nucleic acids, lipopolysaccharide (LPS), and phospholipids.
What is the function of the bacterial cell wall?
It provides structural support and protection to the bacterium.
What is the role of Sulphur in cells?
Component of several amino acids and coenzymes.
What is the role of the plasma membrane in bacteria?
It regulates the movement of substances in and out of the cell.
What is the importance of Potassium in cells?
It is an important inorganic cation and enzyme cofactor.
What is the purpose of ribosomes in a bacterium?
Ribosomes are responsible for protein synthesis.
