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Questions and Answers
If a bacterium thrives in a neutral to slightly acidic environment with a pH range of 5.5 to 8.0, and requires a damp environment, which of the following conditions would most likely inhibit its growth?
If a bacterium thrives in a neutral to slightly acidic environment with a pH range of 5.5 to 8.0, and requires a damp environment, which of the following conditions would most likely inhibit its growth?
- Exposed to a moist, neutral environment with a pH of 7.0.
- An arid and alkaline environment with a pH of 9.0. (correct)
- Stored in a humid environment with a pH of 7.0.
- Submerged in a solution with a pH of 6.5.
A bacterium is found to have a complex outer membrane containing lipopolysaccharides that produce endotoxins, along with a thin peptidoglycan layer. Which of the following is consistent with these bacterial characteristics?
A bacterium is found to have a complex outer membrane containing lipopolysaccharides that produce endotoxins, along with a thin peptidoglycan layer. Which of the following is consistent with these bacterial characteristics?
- It is Gram-positive.
- It is Gram-variable.
- It lacks a cell wall.
- It is Gram-negative. (correct)
A research team is studying a newly discovered bacterium from a deep-sea vent. It thrives at temperatures between 75°C and 90°C. Based on this information, how should this bacterium be classified?
A research team is studying a newly discovered bacterium from a deep-sea vent. It thrives at temperatures between 75°C and 90°C. Based on this information, how should this bacterium be classified?
- Mesophilic
- Psychrophilic
- Thermophilic
- Hyperthermophilic (correct)
In a bacterial cell, if the ribosomes were non-functional, which of the following processes would be most directly affected?
In a bacterial cell, if the ribosomes were non-functional, which of the following processes would be most directly affected?
A bacterium is treated with a dye during Gram staining and appears purple under a microscope. What can be concluded about the structure of this bacterium's cell wall?
A bacterium is treated with a dye during Gram staining and appears purple under a microscope. What can be concluded about the structure of this bacterium's cell wall?
A researcher is studying a bacterium that can survive both in the presence and absence of oxygen. Under anaerobic conditions, what metabolic pathway is this bacterium most likely to utilize?
A researcher is studying a bacterium that can survive both in the presence and absence of oxygen. Under anaerobic conditions, what metabolic pathway is this bacterium most likely to utilize?
If a bacterium is described as a chemoautotroph, what does this indicate about its metabolism?
If a bacterium is described as a chemoautotroph, what does this indicate about its metabolism?
Which structural component of a bacterial cell is most directly associated with its ability to adhere to surfaces and colonize host tissues?
Which structural component of a bacterial cell is most directly associated with its ability to adhere to surfaces and colonize host tissues?
Which of the following is NOT a function associated with the bacterial capsule?
Which of the following is NOT a function associated with the bacterial capsule?
If a bacterial species lacks a nuclear membrane and membrane-bound organelles, how should it be classified?
If a bacterial species lacks a nuclear membrane and membrane-bound organelles, how should it be classified?
Flashcards
Bacteria
Bacteria
Small, single-celled micro-organisms, ancient life forms with basic functions but lacking chlorophyll.
Saprobes
Saprobes
Feed on dead organic matter.
Chemoautotroph
Chemoautotroph
Oxidize inorganic matter (like iron or sulfur) to make food.
Cocci
Cocci
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Bacilli
Bacilli
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Aerobic
Aerobic
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Anaerobic
Anaerobic
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Facultative Aerobic
Facultative Aerobic
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Gram-Positive
Gram-Positive
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Gram-Negative
Gram-Negative
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Study Notes
- Bacteria are small, single-celled microorganisms
- They are an ancient life form
- Bacteria perform the same basic functions as other living cells
- They do not have chlorophyll
- Bacteria usually possess a single, circular DNA chromosome inside the cytoplasm
- Prokaryotic microbes lacking membrane-bound organelles and a nucleus
Size
- Bacteria length ranges from 0.1 to 10 microns
- Bacteria width ranges from 0.2 to 1 micron
- Bacteria size is about 0.5-5 micrometers
Nutrition
- Saprobes feed on dead organic matter
- Parasites feed on a host cells within
- Photoautotrophs use sunlight to make food
- Chemoautotrophs oxidize inorganic matter like iron or sulfur
Classification
- Bacteria are classified according to morphology (shape)
- Bacteria are classified according to needs of oxygen
- Bacteria are classified according to whether they retain stain
- Bacteria are classified according to heat tolerance
- Bacteria are classified according to pathogenicity
Morphology (Shape)
- Cocci are round or oval shaped
- Bacilli are rod-shaped
- Spirilla are spring-shaped
Oxygen needs
- Aerobic bacteria require oxygen to live
- Anaerobic bacteria do not require oxygen to live
- Facultative aerobic bacteria can adjust in either the presence or absence of oxygen
- Microaerophiles need oxygen to grow, but high concentrations of oxygen poisons them
Staining
- Bacteria are classified by their color after gram staining
Gram Staining
- Gram staining distinguishes and classifies bacteria into two groups
- Gram-positive bacteria appear blue, purple, or violet
- Gram-negative bacteria appear red or pink
- Gram-positive bacteria have a thick peptidoglycan cell wall
- Gram-negative bacteria have a thin peptidoglycan cell wall but a thick lipopolysaccharide layer
Heat tolerance
- Psychrophilic bacteria can survive in extreme cold temperatures (-20 to 20)
- Mesophilic bacteria grow best in moderate temperatures (20-45)
- Thermophilic bacteria can survive in extreme hot temperatures (45-80)
- Hyperthermophilic bacteria thrive in very high temperatures (70-110)
Pathogenicity
- Pathogenic bacteria cause disease in humans
- Non-pathogenic bacteria do not cause disease in humans
Environmental Requirements
- Moisture is required and they often grow in damp environments
- Oxygen
- Carbon dioxide
- Temperature
- pH levels need to be neutral or slightly acidic, neutrophils - 5.5 - 8.0
- Light
- Osmotic effect
- Mechanical stress
Structure
- Flagellum
- Ribosomes
- Cytoplasm
- Nucleotide
- Plasma membrane
- Cell wall
- Capsule
- Pilus
Cell Wall
- It is the outermost structure, located outside the cell membrane
- Transparent, tough, and flexible
- Made of Petptidoglycan
- The inner layer of peptidoglycan is thicker in gram-positive bacteria than gram-negative
- Gram-negative bacteria have a complex outer membrane of lipopolysaccharide that produces endotoxins
Plasma Membrane
- Located inside the cell wall and surrounds the cytoplasm, just inside the peptidoglycan layer
- Bacteria cell membrane is made of a lipid bilayer
- Compact and flexible
- It is similar to eurkaryote phospholipid layer but bacteria do not contain sterols
Cytoplasm
- A gel-like substance is enclosed within the cell membrane
- Composed of water, proteins, lipids, nucleic acids, and inorganic salts
- Most metabolic activities take place here
Ribosomes
- Large protein RNA machines that translate genetic information into proteins
- Ribosomes are made of 2 subunits
- Ribosomes receive and translate genetic instructions for protein formation
- Ribosomes can be quickly degraded under stress conditions
Nucleotide
- Contains nucleoid
- A piece of double-stranded DNA without a nuclear membrane or nucleolus
- Contains the genes necessary for activities and traits such as growth, metabolism, reproduction, heredity, and mutation
Capsule
- A layer of slime outside the bacterial cell wall
- Made of polysaccharides and protein
- It is an important virulence factor that protects bacteria from engulfment by eukaryotic immune cells
- Helps bacteria adhere to surfaces
Flagellum
- Whiplike structure
- 'Locomotive organelle' that moves bacteria
- Consists of 3 parts: basal body, hook, and filament
- Involved in the pathogenesis of some diseases and is antigenic
Pilus
- Fine and hair-like
- Shorter than flagella
- Found on the surface of gram-positive bacteria and some gram-negative bacteria
- Associated with bacterial adhesion, colonization, and infection
- Mediate adhesion of bacteria to human cells
- Pili do not move bacteria
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