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While predominantly unicellular, certain bacterial species exhibit the capacity for forming complex multicellular structures.
Answer: True
Explanation: While most bacteria are unicellular, some species, like myxobacteria, can form complex multicellular structures such as fruiting bodies. Others aggregate in pairs, chains, or clusters.
The term 'bacteria' is derived from the Ancient Greek word 'baktērion,' signifying 'staff' or 'cane,' a nomenclature inspired by the prevalent rod-like morphology observed in early discoveries.
Answer: True
Explanation: The word 'bacteria' originates from the Ancient Greek word 'baktērion,' meaning 'staff' or 'cane,' referencing the rod-like shape of many early observed bacteria.
What is the typical size range for most bacteria?
Answer: 0.5 to 5.0 micrometres
Explanation: Most bacteria typically range in size from 0.5 to 5.0 micrometres in length.
The name 'bacteria' comes from the Greek word 'baktērion,' meaning:
Answer: Staff or cane
Explanation: The name 'bacteria' derives from the Greek word 'baktērion,' which translates to 'staff' or 'cane'.
What are the most common shapes of bacterial cells?
Answer: Spherical (cocci) and rod-shaped (bacilli)
Explanation: The most prevalent shapes for bacterial cells are spherical (cocci) and rod-shaped (bacilli).
Bacteria inhabit an extensive array of environments beyond soil and water, including extreme conditions such as hot springs, the deep biosphere, and association with diverse organisms.
Answer: True
Explanation: Bacteria inhabit nearly every possible environment on Earth, including extreme conditions like acidic hot springs, the deep biosphere, and radioactive waste, as well as associations with plants and animals.
A significant proportion of bacterial diversity remains uncultured, necessitating molecular techniques for their study and classification.
Answer: True
Explanation: A significant portion of bacterial diversity cannot be cultured in laboratories, highlighting the importance of molecular methods for studying these organisms.
Bacteria are pivotal in nutrient cycles, playing essential roles in decomposition and nitrogen fixation, far exceeding a minor contribution.
Answer: True
Explanation: Bacteria play a vital role in nutrient cycles, including decomposition and nitrogen fixation.
Which of the following is NOT a habitat where bacteria can be found?
Answer: The vacuum of outer space
Explanation: Bacteria inhabit diverse environments on Earth, including extreme conditions and associations with other organisms, but not the vacuum of outer space.
What vital role do bacteria play in nutrient cycles?
Answer: They are responsible for converting atmospheric nitrogen into usable forms and decomposing dead organisms.
Explanation: Bacteria are crucial for nutrient cycles, facilitating decomposition and converting atmospheric nitrogen into usable forms for other organisms.
How do extremophile bacteria contribute to life in extreme environments like hydrothermal vents?
Answer: They convert dissolved compounds like hydrogen sulphide into energy to sustain life.
Explanation: Extremophile bacteria in environments like hydrothermal vents utilize chemosynthesis, converting dissolved compounds such as hydrogen sulfide into energy.
How does the total biomass of bacteria on Earth compare to that of plants?
Answer: Bacterial biomass is second only to plants.
Explanation: The total biomass of bacteria on Earth is substantial, ranking second only to that of plants.
What is the significance of the 'uncultured microbial majority'?
Answer: It highlights the vast diversity of bacteria that cannot be grown in laboratory conditions, requiring molecular methods for study.
Explanation: The 'uncultured microbial majority' refers to the vast diversity of bacteria that cannot be cultivated in labs, necessitating molecular methods for their study.
In the context of bacterial behavior, 'taxes' denote directed movements in response to environmental stimuli, such as chemotaxis, phototaxis, or magnetotaxis, and are distinct from binary fission, which is a reproductive process.
Answer: True
Explanation: Taxes in bacteria refer to directed movements in response to environmental stimuli, such as chemical gradients (chemotaxis) or light (phototaxis), not binary fission.
The principal structural component of bacterial cell walls is peptidoglycan, a polymer distinct from chitin, which is found in fungi, or cellulose, found in plants.
Answer: True
Explanation: The primary component of bacterial cell walls is peptidoglycan, which differs from chitin found in fungi.
Gram-positive bacteria possess a thick peptidoglycan layer, whereas Gram-negative bacteria are characterized by a thinner peptidoglycan layer situated between the cytoplasmic membrane and an outer membrane.
Answer: True
Explanation: Gram-positive bacteria have a thick peptidoglycan layer, while Gram-negative bacteria have a thinner layer and an outer membrane.
Endospores are highly resistant, dormant structures produced by certain Gram-positive bacteria, such as species of *Bacillus* and *Clostridium*, to endure adverse environmental conditions.
Answer: True
Explanation: Endospores are resistant structures formed by certain Gram-positive bacteria, like *Bacillus* and *Clostridium*, to survive harsh conditions.
Flagella are primarily responsible for bacterial motility, functioning as propulsive organelles; genetic material transfer is typically mediated by pili or other mechanisms.
Answer: True
Explanation: Flagella are primarily used for bacterial motility, not for the transfer of genetic material.
Quorum sensing is a sophisticated intercellular communication system enabling bacteria to synchronize gene expression and collective behaviors in response to population density.
Answer: True
Explanation: Quorum sensing is a communication mechanism bacteria use to coordinate behavior based on population density.
What is a key difference between bacterial (prokaryotic) cells and eukaryotic cells?
Answer: Bacterial cells lack membrane-bound organelles like mitochondria, which are present in eukaryotic cells.
Explanation: A key distinction is that prokaryotic bacterial cells lack membrane-bound organelles, such as mitochondria, which are characteristic of eukaryotic cells.
What is the primary component of bacterial cell walls that provides structural integrity?
Answer: Peptidoglycan
Explanation: Peptidoglycan is the primary component providing structural integrity to bacterial cell walls.
The distinction between Gram-positive and Gram-negative bacteria is based on their reaction to the Gram stain, which correlates with differences in their:
Answer: Cell wall structure
Explanation: The Gram stain differentiates bacteria based on their cell wall structure, specifically the thickness of the peptidoglycan layer.
What are S-layers on bacterial cells primarily composed of?
Answer: Proteins
Explanation: S-layers, the outermost cell envelope component in many bacteria, are primarily composed of proteins.
Which structures are primarily responsible for bacterial motility, functioning like a propeller?
Answer: Flagella
Explanation: Bacterial flagella are the primary structures responsible for motility, functioning rotationally like a propeller.
What is the function of fimbriae in bacteria?
Answer: To aid in attachment to surfaces or host cells
Explanation: Fimbriae are protein appendages that primarily function in bacterial attachment to surfaces or host cells.
A glycocalyx, such as a capsule, can protect bacteria from:
Answer: Host immune cells
Explanation: A bacterial glycocalyx, particularly a capsule, can protect the cell from being engulfed by host immune cells.
Which bacterial genera are known for producing highly resistant endospores?
Answer: *Bacillus* and *Clostridium*
Explanation: The bacterial genera *Bacillus* and *Clostridium* are known for producing highly resistant endospores.
How do bacteria like *Listeria* and *Shigella* move within host cells?
Answer: By hijacking the host cell's cytoskeleton to propel themselves.
Explanation: Bacteria such as *Listeria* and *Shigella* move within host cells by manipulating the host cell's cytoskeleton, particularly actin polymerization.
Autotrophic bacteria synthesize their own cellular carbon, primarily by fixing inorganic carbon dioxide, whereas heterotrophic bacteria utilize pre-formed organic compounds.
Answer: True
Explanation: Autotrophic bacteria obtain their carbon by fixing inorganic compounds such as carbon dioxide, while heterotrophic bacteria utilize organic compounds.
The predominant mode of bacterial reproduction is asexual, primarily through binary fission, rather than sexual reproduction involving gamete fusion.
Answer: True
Explanation: Most bacteria reproduce asexually via binary fission, a process where a single cell divides into two identical daughter cells.
Horizontal gene transfer, a significant mechanism for genetic exchange in bacteria, encompasses processes such as transformation (uptake of exogenous DNA), transduction (mediated by bacteriophages), and conjugation (direct cell-to-cell contact).
Answer: True
Explanation: Horizontal gene transfer in bacteria occurs through three primary mechanisms: transformation, transduction, and conjugation.
Phototrophic bacteria utilize light energy for metabolic processes, whereas chemotrophic bacteria obtain energy via the oxidation of chemical compounds.
Answer: True
Explanation: Phototrophic bacteria obtain energy from light, while chemotrophic bacteria obtain energy from chemical compounds.
Lithotrophs utilize inorganic compounds as electron donors, while organotrophs employ organic compounds for this role in their metabolic pathways.
Answer: True
Explanation: Lithotrophs use inorganic compounds as electron donors, whereas organotrophs use organic compounds.
The majority of bacteria inhabiting the human body are commensal or beneficial, rather than pathogenic; pathogenic species are managed by the host's immune system and other microbial populations.
Answer: True
Explanation: Most bacteria found in or on the human body are harmless or beneficial, contributing to processes like digestion. Pathogenic bacteria are a minority and are typically controlled by the host's immune system.
Penicillin exerts its bactericidal effect by inhibiting the synthesis of peptidoglycan, a critical component of the bacterial cell wall, leading to osmotic lysis.
Answer: True
Explanation: Penicillin inhibits the synthesis of peptidoglycan, a vital component of the bacterial cell wall, thereby weakening the cell wall and leading to bacterial death.
Biofilms, complex microbial communities attached to surfaces, pose significant medical challenges due to their inherent resistance to eradication and association with chronic infections.
Answer: True
Explanation: Biofilms are medically significant because they are difficult to eradicate and are often associated with chronic infections.
DNA-based diagnostic tools, such as PCR, offer advantages in speed and specificity over traditional culture methods for bacterial identification, and can detect non-culturable organisms.
Answer: True
Explanation: DNA-based diagnostic tools are generally faster and more specific than traditional culture methods for bacterial identification and can detect non-culturable bacteria.
*Escherichia coli* (E. coli) stands as the most extensively researched bacterium, evidenced by over 300,000 publications. Intriguingly, a quarter of its genome remains poorly characterized despite this intense scientific scrutiny.
Answer: True
Explanation: Despite being the most studied bacterium, *Escherichia coli* has a significant portion of its genes that remain poorly characterized.
Fatal bacterial diseases include cholera, tuberculosis, bubonic plague, and various respiratory infections.
Answer: True
Explanation: Fatal bacterial diseases include cholera, tuberculosis, bubonic plague, and various respiratory infections.
Approximately how many bacteria are estimated to live in or on the human body?
Answer: 10^13 to 10^14
Explanation: It is estimated that between 10^13 and 10^14 bacterial cells reside in or on the human body.
Which of the following is a common fatal bacterial disease?
Answer: Tuberculosis
Explanation: Tuberculosis is a common fatal bacterial disease, alongside others like cholera and bubonic plague.
In which industrial process are bacteria NOT typically utilized according to the source?
Answer: Manufacturing of synthetic polymers
Explanation: Bacteria are commonly utilized in sewage treatment, oil spill remediation, and the production of fermented foods, but not typically in the manufacturing of synthetic polymers.
Which bacterium is the most extensively studied, with over 300,000 publications?
Answer: *Escherichia coli* (E. coli)
Explanation: *Escherichia coli* (E. coli) is the most extensively studied bacterium, with over 300,000 publications.
How does penicillin exert its antibacterial effect?
Answer: By inhibiting the synthesis of peptidoglycan in the cell wall.
Explanation: Penicillin inhibits the synthesis of peptidoglycan, compromising the bacterial cell wall and leading to cell death.
Which of the following is a beneficial role of gut flora in humans?
Answer: Synthesizing essential vitamins like vitamin K
Explanation: Beneficial roles of gut flora include the synthesis of essential vitamins, such as vitamin K.
The scientific discipline dedicated to the study of bacteria is termed bacteriology, not virology, and it is a branch of microbiology.
Answer: True
Explanation: The scientific study of bacteria is known as bacteriology, a specialized branch within the broader field of microbiology.
Ferdinand Cohn is recognized as a founder of bacteriology for his extensive morphological studies. The discovery of the first antibiotic, Salvarsan, is attributed to Paul Ehrlich in 1910.
Answer: True
Explanation: Ferdinand Cohn is considered a founder of bacteriology for his morphological classifications. The first antibiotic, Salvarsan, was developed by Paul Ehrlich in 1910.
The prevailing theory posits that eukaryotic cells evolved from ancient bacteria through endosymbiotic events, specifically the engulfment of alphaproteobacterial symbionts to form mitochondria.
Answer: True
Explanation: Eukaryotic cells are theorized to have evolved from ancient bacteria via endosymbiosis, with the engulfment of alphaproteobacterial symbionts leading to the formation of mitochondria.
Bacterial classification incorporates criteria such as energy source, electron donors, and carbon source, alongside their oxygen requirements (aerobic vs. anaerobic).
Answer: True
Explanation: Bacterial metabolism is classified based on energy source, electron donors, and carbon source, in addition to their oxygen requirements.
While Louis Pasteur was instrumental in establishing the germ theory of disease, Robert Koch developed Koch's postulates, a rigorous framework for demonstrating that a specific microorganism causes a particular disease.
Answer: True
Explanation: Louis Pasteur advocated for the germ theory of disease, while Robert Koch developed Koch's postulates to establish causal links between specific microbes and diseases.
The International Committee on Systematic Bacteriology (ICSB) governs the standardized nomenclature and classification of bacteria, ensuring taxonomic consistency through adherence to the International Code of Nomenclature of Bacteria.
Answer: True
Explanation: The International Committee on Systematic Bacteriology (ICSB) governs the rules for naming and classifying bacteria, ensuring taxonomic consistency.
In contemporary biological classification, bacteria are recognized as prokaryotes, distinct from plants, and are divided into the domains Bacteria and Archaea.
Answer: True
Explanation: Bacteria are classified as prokaryotes, distinct from plants, and form their own domain within the three-domain system of life.
The evolutionary origins of bacteria are traced to the earliest life forms on Earth, with their ancestors estimated to have emerged approximately 4 billion years ago.
Answer: True
Explanation: Bacterial ancestors are considered among the earliest life forms on Earth, appearing approximately 4 billion years ago.
What is the scientific study of bacteria called?
Answer: Bacteriology
Explanation: The scientific study of bacteria is known as bacteriology.
Historically, how were bacteria classified before the understanding of prokaryotes?
Answer: As plants (Schizomycetes)
Explanation: Historically, bacteria were classified as plants, specifically under the designation Schizomycetes.
What is the estimated age of the earliest bacterial ancestors on Earth?
Answer: Approximately 4 billion years ago
Explanation: The earliest bacterial ancestors are estimated to have appeared on Earth approximately 4 billion years ago.
The formation of mitochondria in eukaryotic cells is thought to have involved which type of ancient bacteria?
Answer: Alphaproteobacterial symbionts
Explanation: The formation of mitochondria in eukaryotic cells is hypothesized to have resulted from the endosymbiotic engulfment of alphaproteobacterial symbionts.
What is the primary method used for modern bacterial classification?
Answer: Molecular systematics and DNA sequencing
Explanation: Modern bacterial classification primarily relies on molecular systematics and DNA sequencing techniques.
Antonie van Leeuwenhoek is considered the first microbiologist because he was the first to:
Answer: Observe bacteria using a microscope
Explanation: Antonie van Leeuwenhoek is recognized as the first microbiologist for his pioneering observations of bacteria using a microscope.