Questions and Answers
What are the most common shapes of bacteria (and describe them)?
Coccus (round and spherical), Diplococcus (two cocci), Bacillus (rod shape), Vibrio (comma shape), Spirillum (chunky worm shape), Spirochetes (corkscrew shape).
What are some differences between a spirillum and spirochete?
The spirillum is shorter than the spirochete, which is longer and more tightly wound. The spirillum has flagella that stick out at both ends, while the spirochete has internal flagella for movement.
What is the shape of the gram (-) Haemophilus influenza, that causes upper respiratory illnesses like pneumonia?
Coccus
What is the shape of the gram (-) Bordetella pertussis, that causes pertussis?
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What is the shape of Treponema pallidum, that causes syphilis?
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What is the shape of Vibrio cholera, that is gram (-)?
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The process of a gram stain involves which two types of cells?
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What is the importance of the gram stain?
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What is an example of a bacteria with no cell wall?
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What color is a gram positive cell?
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What color is the gram negative cell?
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What is the stain for gram positive cells?
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What is the stain for gram negative cells?
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What are the differences in the structures of the gram negative and gram positive bacteria?
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Is E. coli gram negative or gram positive?
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True or false: E. coli is an Enteric?
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Are all Enterics classified as gram positive rod-shaped bacteria or gram negative rod-shaped bacteria?
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What is the shape of E. coli?
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Is Bacillus anthracis gram negative or gram positive?
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What is the shape of Bacillus anthracis, that causes anthrax?
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Is Staphylococcus aureus gram negative or gram positive?
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What is the shape of Staphylococcus aureus?
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Is Streptococcus pyogenes gram negative or gram positive?
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What is the shape of Streptococcus pyogenes?
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Is Neisseria gonorrhea gram negative or gram positive?
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What is the shape of Neisseria gonorrhea?
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List 5 gram negative bacteria.
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List 5 gram positive bacteria.
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What is the evolutionary advantage of endospores?
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What temperature and what time can bacterial spores survive in?
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What are the three genera that can make endospores?
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Are Bacillus and Clostridium spore formers gram positive rods or gram negative rods?
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What is the name of the bacteria thermophile that is used in testing the function of autoclaves?
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Compare and contrast the two genera of spore formers Bacillus and Clostridium.
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What is the MOA of penicillin?
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Name 6 antibiotics that act by inhibiting peptidoglycan biosynthesis.
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Describe the nature of bacterial growth.
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What is a capsule?
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What is flagella?
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What are pili or fimbriae two main functions?
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Why is peptidoglycan important?
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What is peptidoglycan?
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True or False: The formation of the transpeptide bond carried out by transpeptidase is accompanied by the loss of D-ala?
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What is the importance of the Di-aa in the formation of peptidoglycan?
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What is the alternative structure instead of a D-ala D-ala link in peptidoglycan?
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True or false: D-amino acids are rare; most aa are L-aa thus cell wall is one of few places a D-ala is found.
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How do Beta lactams work?
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True or False: Beta lactams bind covalently to a serine in this active site; the beta lactam gets stuck within the transpeptidase making it a suicide inhibitor.
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What is the MOA for cycloserine?
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What is LPS?
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Where is LPS found in gram (-) or gram (+) bacteria?
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What is the toxic portion of LPS?
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How is energy made?
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What is the essential element found in the greatest amount for bacteria metabolism?
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What are some essential elements for bacteria metabolism?
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Where would you find sulfur in bacteria that is essential?
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What is a way that bacteria make energy?
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Besides energy production, what is another use of carbon containing substrates?
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What is fermentation?
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What is respiration?
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What are some fermentation products?
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During the process of fermentation, what will E. coli convert glucose to?
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What genus of bacteria makes only one type of product?
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What are the consequences of fermentation?
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In respiration, where the TCA is functional (unlike in fermentation), what acts as the electron receptor?
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What are some consequences of respiration?
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What does strict aerobe mean and what is a bacteria that is an example of a strict aerobe?
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What does facultative mean and what is a bacteria that is an example of it?
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What does strict anaerobe mean and what is a bacteria that is an example of it?
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What does microaerophilic mean and what is an example of that in bacteria?
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In bacterial growth what is the lag phase?
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In bacterial growth what is the log phase?
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In bacterial growth what is the stationary phase?
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When are endospores made?
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How do bacterial spores work?
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As a consequence of not canning food properly what is an example of a bacteria that could kill you and grow in the food?
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What is a plasmid?
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What is a phage?
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When a phage can insert in chromosome, and not cause cell death what is it called?
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When a phage can replicate in cytoplasm and make phage particles, destroys cell and spreads what is it called?
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Are bacteria haploid or diploid?
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True or false: Bacillus anthracis carries 3 toxin genes on a plasmid (and not on chromosome).
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True or false: Diphtheria toxin and botulinum toxins are both coded by a lysogenic phage.
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Corynebacterium diphtheriae, which causes diphtheria, is gram negative or gram positive?
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What are mutations?
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What are silent mutations?
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What are missense mutations?
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True or false: Some missense mutations are conservative.
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What is a mutation that converts an amino acid codon into a stop codon?
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What is the difference between nonsense and missense mutations?
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What is the mutation that causes a change in the reading frame due to deletion or insertion of a base?
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What are the causes of mutations?
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What breaks down lactose to glucose and galactose?
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What is the diauxic growth on glucose and lactose?
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What are the two important genes in the lac operon related to lactose metabolism?
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What is the regulator component of the lac operon?
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Explain negative regulation in the lac operon.
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What makes the inducer allolactose?
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Again explain the negative regulation of the lac operon.
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Study Notes
Bacterial Shapes and Characteristics
- Bacteria commonly exist in various shapes:
- Coccus: round and spherical
- Diplococcus: two cocci, often with flattened contact points
- Bacillus: rod-shaped
- Vibrio: comma-shaped
- Spirillum: chunky worm-shaped
- Spirochetes: corkscrew-shaped
- Gram (-) bacteria such as Haemophilus influenzae are typically coccus-shaped, while Bordetella pertussis is coccobacillus-shaped.
- Treponema pallidum, causing syphilis, is a spirochete.
- Vibrio cholerae is vibrio-shaped and gram (-).
Gram Staining and Implications
- Gram staining helps identify bacteria:
- Gram positive cells appear purple due to crystal-iodine complex
- Gram negative cells appear pink after counter-staining with safranin.
- Important for determining bacterial classification and guiding antibiotic treatment.
Peptidoglycan and Cell Wall Structures
- Gram positive bacteria have a thicker peptidoglycan layer, while gram negative have a thinner layer and an outer membrane.
- Peptidoglycan consists of alternating N-acetyl muramic acid (NAM) and N-acetyl glucosamine (NAG) linked by amino acids.
- Peptidoglycan cross-linking is essential for maintaining bacterial structure; D-amino acids play a vital role.
Endospores and Survival Mechanisms
- Endospores developed by Bacillus and Clostridium genera allow survival in extreme environments, forming when conditions are unfavorable.
- Geobacillus stearothermophilus is a thermophile used in autoclave efficiency tests, demonstrating spore-forming capabilities.
Antibiotics and Mechanisms of Action
- Penicillin disrupts peptidoglycan biosynthesis by irreversibly binding to transpeptidase.
- Beta-lactam antibiotics share structural similarity with D-Ala-D-Ala, inhibiting the transpeptidation reaction.
Bacterial Metabolism and Energy Production
- Bacteria primarily obtain energy through respiration or fermentation, with carbon as the essential element for metabolism.
- Fermentation operates anaerobically, producing by-products like acetate, ethanol, and lactic acid, with lower ATP yields compared to respiration.
- Strict aerobes such as Pseudomonas aeruginosa rely solely on respiration, while facultative organisms like E. coli can respire or ferment based on oxygen availability.
Gene Regulation in the Lac Operon
- The lac operon is pivotal for lactose metabolism, involving key genes Lac Z (beta-galactosidase) and Lac Y (permease).
- Negative regulation occurs via a repressor that binds the operator unless allolactose (the inducer) is present, promoting transcription.
- Positive regulation, activated under nutrient scarcity, requires CAP binding with cAMP to enhance transcription.
Mutations and Genetic Variability
- Mutations encompass any DNA sequence changes, classified as silent (no amino acid change), missense (amino acid change), nonsense (premature stop codon), or frameshift (disruption of reading frame).
- Common mutation causes include UV light, radiation, chemical mutagens, and DNA polymerase errors.
Specialized Bacteria and Properties
- Mycoplasma lacks a cell wall, affecting antibiotic sensitivity.
- Lactobacillus exhibits unique fermentation patterns, producing only lactate.
- Clostridium botulinum can grow in improperly canned foods, highlighting health hazards related to spore-forming bacteria.
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Description
Test your knowledge on bacterial shapes and characteristics including the various forms of bacteria such as cocci, bacilli, and spirilla. Understand the implications of gram staining in identifying and classifying bacteria, as well as how peptidoglycan affects cell wall structure. Perfect for students studying microbiology.