Bacterial Shapes and Gram Staining Quiz
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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?

<p>Coccobacillus</p> Signup and view all the answers

What is the shape of Treponema pallidum, that causes syphilis?

<p>Spirochete</p> Signup and view all the answers

What is the shape of Vibrio cholera, that is gram (-)?

<p>Vibrio</p> Signup and view all the answers

The process of a gram stain involves which two types of cells?

<p>Gram positive and Gram negative</p> Signup and view all the answers

What is the importance of the gram stain?

<p>It is important for identifying bacteria.</p> Signup and view all the answers

What is an example of a bacteria with no cell wall?

<p>Mycoplasma</p> Signup and view all the answers

What color is a gram positive cell?

<p>Purple</p> Signup and view all the answers

What color is the gram negative cell?

<p>Pink</p> Signup and view all the answers

What is the stain for gram positive cells?

<p>Crystal and iodine</p> Signup and view all the answers

What is the stain for gram negative cells?

<p>Safranin</p> Signup and view all the answers

What are the differences in the structures of the gram negative and gram positive bacteria?

<p>Gram positive bacteria have a thicker peptidoglycan cell wall while gram negative bacteria have a thinner layer of peptidoglycan and possess an outer membrane.</p> Signup and view all the answers

Is E. coli gram negative or gram positive?

<p>Gram (-)</p> Signup and view all the answers

True or false: E. coli is an Enteric?

<p>True</p> Signup and view all the answers

Are all Enterics classified as gram positive rod-shaped bacteria or gram negative rod-shaped bacteria?

<p>Gram - rod bacteria</p> Signup and view all the answers

What is the shape of E. coli?

<p>Bacillus shape</p> Signup and view all the answers

Is Bacillus anthracis gram negative or gram positive?

<p>Gram (+)</p> Signup and view all the answers

What is the shape of Bacillus anthracis, that causes anthrax?

<p>Bacillus shape</p> Signup and view all the answers

Is Staphylococcus aureus gram negative or gram positive?

<p>Gram (+)</p> Signup and view all the answers

What is the shape of Staphylococcus aureus?

<p>Coccus</p> Signup and view all the answers

Is Streptococcus pyogenes gram negative or gram positive?

<p>Gram (+)</p> Signup and view all the answers

What is the shape of Streptococcus pyogenes?

<p>Coccus</p> Signup and view all the answers

Is Neisseria gonorrhea gram negative or gram positive?

<p>Gram (-)</p> Signup and view all the answers

What is the shape of Neisseria gonorrhea?

<p>Coccus</p> Signup and view all the answers

List 5 gram negative bacteria.

<p>E. coli, Neisseria gonorrhea, Haemophilus influenza, Bordetella pertussis, Vibrio cholera</p> Signup and view all the answers

List 5 gram positive bacteria.

<p>Bacillus anthracis, Staphylococcus aureus, Streptococcus pyogenes, Lactobacillus, Enterococcus</p> Signup and view all the answers

What is the evolutionary advantage of endospores?

<p>They can survive in more extreme conditions and resist antiseptics and disinfectants much better and they can last in the soil for months.</p> Signup and view all the answers

What temperature and what time can bacterial spores survive in?

<p>They can tolerate 85 degrees C for 15 minutes.</p> Signup and view all the answers

What are the three genera that can make endospores?

<p>Bacillus, Geobacillus, Clostridium</p> Signup and view all the answers

Are Bacillus and Clostridium spore formers gram positive rods or gram negative rods?

<p>True</p> Signup and view all the answers

What is the name of the bacteria thermophile that is used in testing the function of autoclaves?

<p>Geobacillus stearothermophilus</p> Signup and view all the answers

Compare and contrast the two genera of spore formers Bacillus and Clostridium.

<p>They are both gram positive spore-forming rods, but Clostridium is an anaerobe while Bacillus is an aerobe.</p> Signup and view all the answers

What is the MOA of penicillin?

<p>It interferes with the biosynthesis of the peptidoglycan by binding permanently to the transpeptidase enzyme.</p> Signup and view all the answers

Name 6 antibiotics that act by inhibiting peptidoglycan biosynthesis.

<p>Penicillin (Beta-lactam), Cephalosporin (Beta-lactam), Vancomycin, Bacitracin, Isoniazid, Cycloserine.</p> Signup and view all the answers

Describe the nature of bacterial growth.

<p>One cell divides to make two cells, requiring coordination of biosynthesis and replication in quantity and location.</p> Signup and view all the answers

What is a capsule?

<p>It is external material made of either polysaccharide or protein that helps avoid immune and phagocytic activities.</p> Signup and view all the answers

What is flagella?

<p>It is stuck in the cell wall and moves bacteria by acting like a propeller.</p> Signup and view all the answers

What are pili or fimbriae two main functions?

<ol> <li>Sex pili transfer genetic information through conjugation. 2. Adhesion (stick to surfaces for attachment).</li> </ol> Signup and view all the answers

Why is peptidoglycan important?

<p>It allows for differentiation of organisms as Gram +/- and serves as an antibiotic target.</p> Signup and view all the answers

What is peptidoglycan?

<p>A complex structure of interlinked polymers made of N-acetyl muramic acid and N-acetyl glucosamine (NAM &amp; NAG) and amino acids.</p> Signup and view all the answers

True or False: The formation of the transpeptide bond carried out by transpeptidase is accompanied by the loss of D-ala?

<p>True</p> Signup and view all the answers

What is the importance of the Di-aa in the formation of peptidoglycan?

<p>It is essential for the cross-link between peptidoglycan chains.</p> Signup and view all the answers

What is the alternative structure instead of a D-ala D-ala link in peptidoglycan?

<p>It can have the formation of a peptaglycine bridge.</p> Signup and view all the answers

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.

<p>True</p> Signup and view all the answers

How do Beta lactams work?

<p>They prevent the transpeptidase reaction, which is the joining of the D-ala with the di-aa. Beta lactam antibiotics have a 3-D similarity to the D-Ala-D-Ala dimer.</p> Signup and view all the answers

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.

<p>True</p> Signup and view all the answers

What is the MOA for cycloserine?

<p>It interferes with the production of D-ala-D-ala, by inhibiting alanine racemase and D-ala-D-ala synthase.</p> Signup and view all the answers

What is LPS?

<p>Lipopolysaccharide is the outer half of the outer membrane made of Lipid A, core polysaccharide, and O antigen.</p> Signup and view all the answers

Where is LPS found in gram (-) or gram (+) bacteria?

<p>Gram (-)</p> Signup and view all the answers

What is the toxic portion of LPS?

<p>Lipid A can cause fever, shock, and death.</p> Signup and view all the answers

How is energy made?

<p>Respiration or fermentation.</p> Signup and view all the answers

What is the essential element found in the greatest amount for bacteria metabolism?

<p>Carbon</p> Signup and view all the answers

What are some essential elements for bacteria metabolism?

<p>N, P, and S in moderate amounts; Zn, Mn, Mo, Co in small amounts.</p> Signup and view all the answers

Where would you find sulfur in bacteria that is essential?

<p>Methionine and Cysteine (amino acids that contain sulfur).</p> Signup and view all the answers

What is a way that bacteria make energy?

<p>They convert carbon containing substrates to glucose and other end products.</p> Signup and view all the answers

Besides energy production, what is another use of carbon containing substrates?

<p>A source of carbon for cell construction, by biosynthesis of everything in the cell containing carbon.</p> Signup and view all the answers

What is fermentation?

<p>An ATP yielding process, using substrate-level phosphorylation, where INTERNAL electron acceptors are used. Typically O2 is absent.</p> Signup and view all the answers

What is respiration?

<p>An ATP yielding process, using electron transport phosphorylation, where an EXTERNAL compound is used as a terminal electron acceptor. Typically O2 is the electron acceptor.</p> Signup and view all the answers

What are some fermentation products?

<p>Acetate, Ethanol, Butyrate, H2 + CO2, Formate, Propionate, 2,3 Butandiol, Lactic acid.</p> Signup and view all the answers

During the process of fermentation, what will E. coli convert glucose to?

<p>Acetate, H2O2, ethanol (maybe).</p> Signup and view all the answers

What genus of bacteria makes only one type of product?

<p>Lactobacillus</p> Signup and view all the answers

What are the consequences of fermentation?

<p>Less ATP yield per mole glucose than with respiration; fermentation products can be used to identify bacteria; tissue damage by acid or gas.</p> Signup and view all the answers

In respiration, where the TCA is functional (unlike in fermentation), what acts as the electron receptor?

<p>Oxygen</p> Signup and view all the answers

What are some consequences of respiration?

<p>Higher yield of cells per mole glucose than with fermentation; useful for the identification of bacteria.</p> Signup and view all the answers

What does strict aerobe mean and what is a bacteria that is an example of a strict aerobe?

<p>Always uses respiration; an example is Pseudomonas aeruginosa.</p> Signup and view all the answers

What does facultative mean and what is a bacteria that is an example of it?

<p>Can use respiration or fermentation; examples include E. coli and Salmonella typhi.</p> Signup and view all the answers

What does strict anaerobe mean and what is a bacteria that is an example of it?

<p>Always uses fermentation; an example is Clostridium tetani.</p> Signup and view all the answers

What does microaerophilic mean and what is an example of that in bacteria?

<p>Must have less O2 than atmospheric, but always uses respiration; an example is Helicobacter pylori.</p> Signup and view all the answers

In bacterial growth what is the lag phase?

<p>Time of inapparent growth or no growth.</p> Signup and view all the answers

In bacterial growth what is the log phase?

<p>Grows at growth rate.</p> Signup and view all the answers

In bacterial growth what is the stationary phase?

<p>It occurs because max is met that is determined by the amount of supplies.</p> Signup and view all the answers

When are endospores made?

<p>When environmental conditions become unfavorable for growth, e.g. when food runs out.</p> Signup and view all the answers

How do bacterial spores work?

<p>They wall off the DNA, and a few enzymes and ribosomes, into a strong multilayered structure.</p> Signup and view all the answers

As a consequence of not canning food properly what is an example of a bacteria that could kill you and grow in the food?

<p>Clostridium botulinum (gram positive spore forming rod)</p> Signup and view all the answers

What is a plasmid?

<p>A plasmid is a circular piece of DNA that is able to self-replicate with cell division.</p> Signup and view all the answers

What is a phage?

<p>A piece of DNA that is like a bacterial virus.</p> Signup and view all the answers

When a phage can insert in chromosome, and not cause cell death what is it called?

<p>Lysogeny</p> Signup and view all the answers

When a phage can replicate in cytoplasm and make phage particles, destroys cell and spreads what is it called?

<p>Lytic phage</p> Signup and view all the answers

Are bacteria haploid or diploid?

<p>Haploid</p> Signup and view all the answers

True or false: Bacillus anthracis carries 3 toxin genes on a plasmid (and not on chromosome).

<p>True</p> Signup and view all the answers

True or false: Diphtheria toxin and botulinum toxins are both coded by a lysogenic phage.

<p>True</p> Signup and view all the answers

Corynebacterium diphtheriae, which causes diphtheria, is gram negative or gram positive?

<p>Gram positive</p> Signup and view all the answers

What are mutations?

<p>Mutations are any base change in DNA sequence.</p> Signup and view all the answers

What are silent mutations?

<p>A change in the 3rd base of the DNA corresponding to a codon, leading to no change in amino acid.</p> Signup and view all the answers

What are missense mutations?

<p>Mutations that result in an amino acid change due to a base change that is not the wobble base.</p> Signup and view all the answers

True or false: Some missense mutations are conservative.

<p>True</p> Signup and view all the answers

What is a mutation that converts an amino acid codon into a stop codon?

<p>Nonsense mutation</p> Signup and view all the answers

What is the difference between nonsense and missense mutations?

<p>Nonsense has no meaning, while missense means it has a different meaning.</p> Signup and view all the answers

What is the mutation that causes a change in the reading frame due to deletion or insertion of a base?

<p>Frameshift mutation</p> Signup and view all the answers

What are the causes of mutations?

<p>UV light, other radiation, DNA polymerase errors, chemical mutagens.</p> Signup and view all the answers

What breaks down lactose to glucose and galactose?

<p>Beta galactosidase</p> Signup and view all the answers

What is the diauxic growth on glucose and lactose?

<p>If given both, bacteria will use glucose first and then lactose.</p> Signup and view all the answers

What are the two important genes in the lac operon related to lactose metabolism?

<p>Lac Z codes for beta-galactosidase and Lac Y is a permease for transporting lactose.</p> Signup and view all the answers

What is the regulator component of the lac operon?

<p>The promoter directs the Lac I (inhibitor/repressor).</p> Signup and view all the answers

Explain negative regulation in the lac operon.

<p>mRNA transcribed from Lac I converts to a repressor protein that binds to the operator preventing transcription until the inducer allolactose is present.</p> Signup and view all the answers

What makes the inducer allolactose?

<p>Beta galactosidase makes allolactose from lactose.</p> Signup and view all the answers

Again explain the negative regulation of the lac operon.

<p>Lac I transcribes mRNA, translates it into repressor protein which binds to the operator preventing transcription until induced by allolactose.</p> Signup and view all the answers

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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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.

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