Microbial Diversity and Bacterial Anatomy
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Questions and Answers

Which structure is NOT part of the outer structures of bacteria?

  • Flagella
  • Endospores (correct)
  • Pili/Fimbriae
  • Glycocalyx

Eukaryotic pathogens represent the majority of microbial diversity.

False (B)

What is the primary function of ribosomes in bacterial cells?

protein synthesis

Gram-positive bacteria have a thick ______ layer containing teichoic acid.

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

Match the types of bacterial cell structures with their functions:

<p>Nucleoid = Contains bacterial DNA Plasmids = Confer resistance mechanisms Endospores = Survive extreme conditions Flagella = Enable motility</p> Signup and view all the answers

What type of antibiotic is directly sourced from microorganisms?

<p>Natural antibiotics (B)</p> Signup and view all the answers

Antimicrobials can only be derived from natural sources.

<p>False (B)</p> Signup and view all the answers

What does MIC stand for in the context of antibiotic resistance?

<p>Minimal Inhibitory Concentration</p> Signup and view all the answers

The first targeted antimicrobial treatment for syphilis was called __________.

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

Match the antibiotics with their significance:

<p>Penicillin = Revolutionized treatment but foresaw resistance Prontosil = Early sulphonamide antibiotic Salvarsan = First targeted antimicrobial treatment for syphilis Methicillin = Used against resistant Staphylococcus aureus</p> Signup and view all the answers

What color do gram-positive bacteria appear after Gram staining?

<p>Purple (A)</p> Signup and view all the answers

Bacteria enter the Exponential (Log) Phase when they have exhausted their resources.

<p>False (B)</p> Signup and view all the answers

What term describes the increase in cell number or mass over time in bacteria?

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

Bacteria often communicate using ________ to detect population density.

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

Match the bacterial growth phase with its description:

<p>Lag Phase = Cells adapting to environment without growth Exponential Phase = Rapid increase in mass and number Stationary Phase = Growth and death rates are equal Death Phase = Decline due to resource depletion</p> Signup and view all the answers

Which of the following factors can affect bacterial growth?

<p>All of the above (D)</p> Signup and view all the answers

Biofilms can only be formed by single-species bacteria.

<p>False (B)</p> Signup and view all the answers

What are macronutrients required by prokaryotes, and why are they important?

<p>Carbon, nitrogen, phosphorus, sulfur; they are needed in large amounts for macromolecule synthesis.</p> Signup and view all the answers

What is a key mechanism of antibiotic resistance in bacteria?

<p>Altered target site (D)</p> Signup and view all the answers

Conjugation allows for the transfer of genetic material through bacteriophages.

<p>False (B)</p> Signup and view all the answers

Name one example of a key pathogen of concern that exhibits multidrug resistance.

<p>Staphylococcus aureus</p> Signup and view all the answers

The mechanism where bacteria reduce drug accumulation is called ______.

<p>decreased drug accumulation</p> Signup and view all the answers

Match the following pathogens with their associated issues:

<p>Neisseria gonorrhoeae = Increasing untreatable cases Mycobacterium tuberculosis = Dormant infections that can reactivate Plasmodium falciparum = Resistance to all current antimalarial drugs Acinetobacter baumannii = Causes hospital-acquired infections</p> Signup and view all the answers

Which of the following is NOT a source of resistance genes?

<p>Mitochondrial DNA (D)</p> Signup and view all the answers

Horizontal gene transfer can occur through transformation, transduction, and mutation.

<p>False (B)</p> Signup and view all the answers

What do we call the extra-chromosomal DNA that often contains multiple resistance genes?

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

What is one major consequence of increased antibiotic resistance in patients?

<p>Increased mortality (C)</p> Signup and view all the answers

The disruption of the microbiome facilitates the growth of resistant bacterial strains.

<p>True (A)</p> Signup and view all the answers

Name a type of through which MRSA can acquire antibiotic resistance.

<p>horizontal gene transfer</p> Signup and view all the answers

New approaches to combat antibiotic resistance include developing drugs targeting __________ mechanisms.

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

Match the following bacteria with their resistance mechanisms:

<p>MRSA = Acquires Pbp2a through SCCmec element Mycobacterium tuberculosis = Forms persister cells Salmonella typhi = Uses toxin-antitoxin systems S.aureus = Undergoes horizontal gene transfer for resistance</p> Signup and view all the answers

What is a characteristic of persister cells?

<p>They can evade the effects of antibiotics. (A)</p> Signup and view all the answers

Beta-lactam resistance can be caused by the degradation of beta-lactams by beta-lactamases.

<p>True (A)</p> Signup and view all the answers

Which system involves both toxins and antitoxins?

<p>toxin-antitoxin systems</p> Signup and view all the answers

What significant impact did the discovery of antibiotics in the 1930s have on life expectancy?

<p>Increased it by 8 years (C)</p> Signup and view all the answers

Antimicrobial resistance emerged shortly after penicillin's introduction.

<p>True (A)</p> Signup and view all the answers

What are the strengths of phenotypic screens?

<p>Good in vivo translation and potential to discover novel biology.</p> Signup and view all the answers

The ideal Z' factor for assessing screen quality is _____.

<p>1</p> Signup and view all the answers

Match the following antibiotic discovery processes with their descriptions:

<p>Primary screen = Safety testing using high-throughput assays Secondary screen = Assessment of bioavailability and toxicity DBT cycles = Iterative design-build-test for optimization Target validation = Confirmation of target engagement</p> Signup and view all the answers

What is a limitation of synthetic small molecules?

<p>Limited chemical diversity (A)</p> Signup and view all the answers

Targets can only be identified through genetic approaches.

<p>False (B)</p> Signup and view all the answers

What does Lipinski's rule of 5 predict?

<p>Drug-like properties for oral bioavailability.</p> Signup and view all the answers

The engagement of a small molecule with its target is referred to as _____.

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

Match the following small molecule sources with their advantages:

<p>Natural products = High stability and selectivity Synthetic small molecules = Ease of synthesis and rapid SAR optimization</p> Signup and view all the answers

What is a key goal of the Target 2035 initiative?

<p>Develop probes for every known target (C)</p> Signup and view all the answers

Target validation ensures the mechanism of action is not related to the observed phenotype.

<p>False (B)</p> Signup and view all the answers

Identify one method used in target identification.

<p>CRISPR knockout.</p> Signup and view all the answers

The interaction of a small molecule with its target is called _____.

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

Which antibiotic resistance trend was noted by the 1970s?

<p>Widespread resistance in common pathogens (C)</p> Signup and view all the answers

What is the objective of biochemical studies in the context of target validation?

<p>To determine how the drug-target interaction produces phenotypic effects.</p> Signup and view all the answers

Flashcards

Glycocalyx

A rigid or deformable outer polysaccharide layer that helps bacteria evade the immune system and cause infection.

Flagella

Whip-like structures made of protein that allow bacteria to move around.

Pili/Fimbriae

Short hair-like appendages that help bacteria stick to surfaces and exchange genetic material.

Endospore

A tough, protective structure formed by some bacteria under stress, allowing them to survive harsh conditions.

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Gram-Positive Bacteria

A bacterial cell wall structure with a thick peptidoglycan layer, teichoic acid, and anchor proteins.

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Antibiotics

Substances derived from microorganisms that kill or inhibit the growth of other microbes.

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Minimal Inhibitory Concentration (MIC)

The lowest concentration of an antibiotic needed to stop the growth of bacteria.

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Antimicrobials

A broad category of drugs that target bacteria, fungi, or viruses. Not all antimicrobials are biologically derived.

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Antibiotic Resistance

Occurs when the required antibiotic concentration to inhibit bacterial growth exceeds the effective threshold, making the antibiotic less effective.

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Antibiotic Prophylaxis

Use of antibiotics to prevent infections, especially in situations like surgeries or organ transplants.

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What is Gram Staining?

A staining technique that categorizes bacteria based on cell wall structure. Gram-positive bacteria have a thick peptidoglycan layer and retain the crystal violet dye, appearing purple under a microscope. Gram-negative bacteria have a thinner peptidoglycan layer and lose the dye, appearing red after counterstaining.

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What is the Cytoplasmic Membrane?

A selective barrier that controls the movement of substances into and out of the bacterial cell. It is composed of a phospholipid bilayer and plays a crucial role in nutrient transport and energy conservation.

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What is Bacterial Growth?

An increase in the number of cells or mass of bacteria over time.

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What is the Lag Phase of Bacterial Growth?

A phase of bacterial growth where cells are adapting to a new environment without immediately dividing. They are actively expressing genes and synthesizing molecules needed for growth.

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What is the Exponential (Log) Phase of Bacterial Growth?

A period of rapid bacterial growth where the population doubles with each generation. This phase is characterized by exponential increases in cell mass and number.

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What is the Stationary Phase of Bacterial Growth?

The phase of bacterial growth where the rate of cell growth equals the rate of cell death. This occurs due to limited resources and an accumulation of waste products.

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What is the Death Phase of Bacterial Growth?

The phase of bacterial growth where the death rate exceeds the growth rate. This occurs due to a complete depletion of resources and a high accumulation of toxic waste products.

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What is Quorum Sensing?

A form of communication between bacteria where they use signaling molecules called autoinducers to sense the local population density. It influences various aspects of bacterial behavior, including the production of virulence factors.

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Antibiotic Resistance Mechanisms

Bacteria develop resistance to antibiotics through various mechanisms, such as altering the target site of the antibiotic, inactivating the antibiotic using enzymes, changing their metabolism to avoid the antibiotic's effect, or reducing the antibiotic's accumulation within the cell.

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Altered Target Site

Mutations and alterations in DNA, specifically the acquisition of genes or enzymes, enable some bacteria to become resistant to antibiotics. This process is often driven by the presence of antibiotics.

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Antibiotic Inactivation

Some bacteria produce enzymes that break down or inactivate antibiotics, rendering them ineffective. Beta-lactamases are a well-known example that degrade penicillin-like antibiotics.

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Horizontal Gene Transfer

Through horizontal gene transfer, bacteria can exchange genetic material, including resistance genes. This transfer can occur through conjugation, transformation, or transduction.

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ESKAPE Pathogens

These pathogens are commonly found in hospitals and often exhibit high levels of multidrug resistance, presenting a significant challenge for healthcare.

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Neisseria gonorrhoeae

A sexually transmitted infection with increasing cases of resistance to antibiotics. This makes it difficult to treat and control the spread.

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Mycobacterium tuberculosis

This bacterium, responsible for tuberculosis, can reside in a dormant state within the body for extended periods. The emergence of extensively drug-resistant strains poses a serious threat.

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Selective Pressure

The spread of drug resistance is driven by selective pressure, where antibiotics favor the survival and replication of resistant bacteria. This creates a cycle of resistance development and spread.

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Beta-Lactamase Resistance

A specific type of antibiotic resistance where bacteria produce enzymes that break down antibiotics.

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Pbp2a (Penicillin-Binding Protein) Resistance

A specific type of resistance seen in MRSA, caused by a mutated protein that prevents antibiotics from binding.

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Persister Cells

Dormant bacterial cells that are resistant to antibiotics. They can revive when conditions are favorable.

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Toxin-Antitoxin Systems

A mechanism by which some bacteria survive antibiotic stress. They contain toxins that halt growth and antitoxins that counteract them.

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TacT (Toxin-Antitoxin System Toxin)

A specific toxin that inhibits bacterial growth, promoting persister formation.

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Methicillin-Resistant Staphylococcus aureus (MRSA)

A specific type of Staphylococcus aureus that is resistant to methicillin and other beta-lactam antibiotics.

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SCCmec (Staphylococcal Cassette Chromosome mec)

A genetic element that carries the gene for the alternate Pbp2a, leading to methicillin resistance in MRSA.

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Narrow-spectrum antibiotic

An antibiotic that targets a specific type of bacteria, limiting its effects on other beneficial bacteria.

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Antimicrobial resistance (AMR)

The ability of bacteria to survive exposure to antibiotics, making them ineffective.

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Drug discovery process

A research process of identifying and developing potential drug candidates.

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Primary screen

Testing a large number of potential drug compounds for their basic properties.

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Secondary screen

A series of tests evaluating a compound's absorption, distribution, metabolism, and excretion.

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DBT cycle

A cycle of designing, building, and testing molecules to optimize their properties.

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Target-based screens

A method of drug discovery focusing on specific target proteins known to be involved in disease.

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Phenotypic screens

A method of drug discovery that analyzes biological outcomes without focusing on specific targets.

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Z factor

A statistical measurement of assay quality, indicating how reliably controls can identify successful drug candidates.

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EC50

The concentration of a drug required to achieve half of its maximum effect.

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Structure-activity relationship (SAR)

The study of how the structure of a molecule relates to its biological activity.

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Natural products

Natural compounds extracted from organisms like plants, microorganisms, and marine animals.

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Lipinski's rule of 5

A set of guidelines predicting oral bioavailability of drug-like molecules.

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Target identification

The process of identifying the specific protein targeted by a drug and how it works.

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Target validation

Confirming that the drug-target interaction is responsible for the observed biological effects.

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Study Notes

Microbial Diversity and Bacterial Anatomy

  • Microbial diversity is vast, with bacteria being the most diverse organisms.
  • Eukaryotic pathogens are a smaller fraction of microbial diversity but can be difficult to target.
  • Bacteria have diverse structures (cocci, bacilli, etc.) but share common features.
  • Prokaryotic cells are divided into outer and inner structures separated by a cytoplasmic membrane.

Outer Structures

  • Glycocalyx (capsule): A polysaccharide layer, either rigid (capsule) or flexible (slime), aiding pathogenicity and immune invasion.
  • Flagella: Protein structures enabling motility, varying in distribution.
  • Pili/fimbriae: Shorter appendages for attachment to surfaces and DNA transfer.

Inner Structures

  • Endospores: Resistant cells formed under stress, able to survive harsh conditions and revert to vegetative cells.
  • Ribosomes: 70S structure (30S and 50S subunits), used for protein synthesis.
  • Nucleoid: Region containing supercoiled bacterial DNA.
  • Plasmids: Separate from chromosomal DNA, conferring resistance mechanisms, and replicating autonomously.

Cell Wall

  • Gram-positive bacteria: Thick peptidoglycan layer, teichoic acid, and anchor proteins.
  • Gram-negative bacteria: Multi-layered cell wall with an outer membrane containing lipopolysaccharide (LPS).
  • Gram staining differentiates these cell walls (gram-positive stains purple, gram-negative red).

Cytoplasmic Membrane

  • Selective barrier (phospholipid bilayer) for nutrient transport and energy conservation.

Population Growth

  • Growth: Increase in cell number or mass over time.
  • Exponential growth is tracked via a growth curve.
    • Lag phase: Adaptation, no growth
    • Exponential phase: Optimal growth
    • Stationary phase: Growth and death rates balance
    • Death phase: Resources depleted, growth ceases

Factors Affecting Growth

  • Influenced by temperature, medium composition, environmental conditions, and nutrient availability.
  • Bacteria exhibit varying metabolic behaviors based on nutrient availability.
  • Quorum sensing: Bacteria communicate and adjust biological processes based on population density.

Biofilms

  • Bacteria can grow in 3D structures, either single or multispecies.
  • Biofilms provide a complex environment for nutrient flow and support.

Prokaryotic Nutrition

  • Macronutrients: Carbon, nitrogen, phosphorus, and sulfur are needed in large amounts for cell components.
  • Micronutrients: Metal ions are required in smaller amounts for enzyme function.

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Description

Explore the vast world of microbial diversity, focusing on the anatomy and structures of bacteria. This quiz covers key concepts such as the functions of outer and inner bacterial structures, including their roles in pathogenicity and survival. Test your knowledge on the diverse forms bacteria take and how they adapt to their environments.

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