Bacterial Cell Structure Quiz
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Questions and Answers

What is the primary structure that distinguishes Gram positive bacteria from Gram negative bacteria?

  • Presence of outer membrane
  • Number of amino acids in tetrapeptide
  • Shape of bacterial cells
  • Thickness of cell wall (correct)

Which component is essential for the cross-linking of the peptidoglycan chain?

  • NAG
  • Di-amino pimelic acid (correct)
  • UDP-NAM
  • Lisine (correct)

What is the process by which NAG is converted to NAM in bacterial cells?

  • Enzymatic conversion (correct)
  • Phosphorylation
  • Hydrolysis
  • Dephosphorylation

What kind of bridge is formed in Gram negative bacteria for peptidoglycan cross-linking?

<p>Direct bridge (C)</p> Signup and view all the answers

Which type of amino acids are found in the tetrapeptide of the peptidoglycan structure?

<p>Both D and L-amino acids (A)</p> Signup and view all the answers

What is responsible for the directional movement of bacterial cells?

<p>Counterclockwise and clockwise rotation (A)</p> Signup and view all the answers

Which structure is primarily composed of the protein subunit pilin?

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

What effect does clockwise rotation of flagella have on bacterial movement?

<p>Change of direction (A)</p> Signup and view all the answers

Which of the following statements about fimbriae is true?

<p>They facilitate adherence to host tissues. (B)</p> Signup and view all the answers

What is one of the roles of the tips of fimbriae?

<p>Binding to specific sugars on host cells (B)</p> Signup and view all the answers

What is the primary structural difference between Gram positive and Gram negative bacteria regarding peptidoglycan layers?

<p>Gram positive bacteria typically have around 40 layers of peptidoglycan, while Gram negative bacteria have 2-3 layers. (A)</p> Signup and view all the answers

Which characteristic best describes the cell wall of Mycobacteria?

<p>It has a complex, lipid-rich structure providing acid-fastness. (C)</p> Signup and view all the answers

What occurs during the Gram staining process to Gram negative bacteria?

<p>Crystal violet is washed away, revealing a red counterstain. (C)</p> Signup and view all the answers

What component is found in the tetrapeptide of Gram positive bacteria?

<p>L-lysine. (D)</p> Signup and view all the answers

Which of the following bacteria is well-known for being visualized as purple when Gram stained?

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

What factors influence the composition of the intestinal microbiota in infants?

<p>Mode of delivery and infant feeding method (A)</p> Signup and view all the answers

Which vitamin is NOT biosynthesized by intestinal microbiota?

<p>Vitamin D (C)</p> Signup and view all the answers

What characterizes the intestinal microbiota of infants?

<p>Low stability and low diversity (A)</p> Signup and view all the answers

What role does fermentation of polysaccharides play in the functions of intestinal microbiota?

<p>Provides energy sources for gut microbes (D)</p> Signup and view all the answers

Which of the following is a consequence of dysbiosis in the gut microbiota?

<p>Increased risk of disease (B)</p> Signup and view all the answers

What is the primary therapeutic application of fecal microbiota transplantation (FMT)?

<p>Transferring healthy gut bacteria (B)</p> Signup and view all the answers

Permanent colonization by microbes is distinguished from transient colonization primarily by:

<p>Duration of microbial presence (B)</p> Signup and view all the answers

What is NOT a function of intestinal microbiota?

<p>Enhancing brain activity (D)</p> Signup and view all the answers

What is one of the main functions of the skin microbiota?

<p>To maintain a healthy cutaneous barrier (B)</p> Signup and view all the answers

Which factor can lead to dysbiosis of the skin microbiota?

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

What structure surrounds a bacterial cell's cytoplasmic membrane?

<p>Cell wall/outer membrane (B)</p> Signup and view all the answers

What is the role of topoisomerases during DNA replication?

<p>To unwind and manage DNA supercoiling (A)</p> Signup and view all the answers

How is bacterial DNA characterized in terms of structure?

<p>Double-stranded and circular (C)</p> Signup and view all the answers

Which enzyme is primarily responsible for initiating the process of DNA replication?

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

What is a unique biochemical target for antibiotic action in bacteria?

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

During DNA replication, new strands are synthesized in which manner?

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

What type of plasmid primarily helps bacteria overcome stressful conditions?

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

What type of genome do bacteria possess?

<p>Haploid without histones (C)</p> Signup and view all the answers

What is required for the rolling circle replication of DNA?

<p>A nicking enzyme (C)</p> Signup and view all the answers

What is the characteristic of plasmids in bacteria?

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

Which topoisomerase is primarily involved in relaxing supercoiled circular DNA at the end of bacterial DNA replication?

<p>Topoisomerase IV (C)</p> Signup and view all the answers

What best describes the structure of DNA in bacteria?

<p>Single, circular, double-stranded and supercoiled (C)</p> Signup and view all the answers

What is the function of DNA-dependent DNA polymerase during DNA replication?

<p>To synthesize a copy of the DNA (D)</p> Signup and view all the answers

In bacterial DNA replication, what mechanism do topoisomerases primarily support?

<p>Supercoiling and relaxation of DNA (C)</p> Signup and view all the answers

Flashcards

Human Microbiota (Normal Flora)

Microorganisms (mainly bacteria) that live in or on our bodies, playing crucial roles in health and disease.

Permanent Colonization

The process where microbes become permanently established in a particular place.

Transient Colonization

The process where microbes temporarily reside somewhere before being eliminated.

Intestinal Microbiota

The collection of microbes living in the intestines, playing vital roles in digestion, immune system, and overall health.

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Mode of Delivery Impact

The process by which the gut microbiome develops differently in infants based on how they are fed: breastfeeding or formula.

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Food Compound Breakdown

The ability of the gut microbiota to break down complex food components that the body can't digest on its own.

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Fecal Microbiota Transplantation (FMT)

The transfer of healthy fecal matter from a donor to a recipient with a dysbiotic gut microbiome, aiming to restore balance.

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Disruption of the Intestinal Microbiota

The process of changing the composition and function of the gut microbiota, often leading to health issues.

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Virulence plasmids

Plasmids that carry genes for traits that allow the bacterium to overcome stressful situations, but are not essential for daily survival.

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Skin Microbiota Density

The skin microbiota is the second largest microbiota of the human body, with a density of 10^6 microbes per square centimeter, totaling 10^8 to 10^10 microbes.

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Skin Microbiota Functions

The skin microbiota plays a crucial role in maintaining a healthy skin barrier, supporting the immune system, and limiting the growth of harmful microorganisms.

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Degradative plasmids

Plasmids that carry genes for traits that help bacteria utilize a new source of nutrients, such as breaking down a specific compound.

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Fertility Plasmids

Plasmids that carry genes responsible for bacterial conjugation, allowing transfer of genetic material between bacteria.

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Skin Microbiota Stabilization

The skin microbiota is constantly changing throughout life, undergoing a significant restructuring during puberty and stabilizing in adulthood.

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Replication origin (oriC)

The specific site on a chromosome where DNA replication begins, acting as a starting point for DNA copying.

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Skin Microbiota Dysbiosis

Dysbiosis, an imbalance in the skin microbiota, can be caused by factors such as environmental influences, cosmetic products, and poor diet.

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Helicase

An enzyme that unwinds and separates the two strands of DNA during replication, allowing access to the bases for copying.

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Bacteria: Prokaryotic

The most abundant type of life on Earth is bacteria, a type of prokaryotic organism that includes various beneficial and harmful species.

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Primase

An enzyme that synthesizes short RNA sequences called primers, which provide a starting point for DNA polymerase to begin copying.

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Bacterial Chromosome

The bacterial chromosome is a single, circular, double-stranded DNA molecule responsible for storing genetic information and directing cellular functions.

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Plasmids: Extra Chromosomal DNA

Plasmids are small, circular DNA molecules that carry extra genes and can be transferred between bacteria.

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Topoisomerases

Enzymes that alter the supercoiling of DNA, either relaxing or tightening the DNA structure.

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Topoisomerases: DNA Compaction

Topoisomerases are enzymes in bacteria that help to compact their DNA by changing its topological structure, making it a target for antibiotics.

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Semiconservative replication

A process where each new DNA molecule consists of one original strand and one newly synthesized strand.

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Gram-positive cell wall

A bacterial cell wall with many layers of peptidoglycan, making it thick and resistant to decolorization during Gram staining.

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Gram-negative cell wall

A bacterial cell wall with few layers of peptidoglycan, making it thin and susceptible to decolorization during Gram staining.

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Mycobacteria

A type of bacteria with a unique cell wall structure rich in lipids, making them resistant to acid, detergents, and antibiotics.

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Gram stain

A staining technique used to classify bacteria based on their cell wall structure.

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Crystal violet precipitation

The process of trapping crystal violet dye in the thick peptidoglycan layer of Gram-positive bacteria during Gram staining.

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Peptidoglycan

A rigid mesh-like structure that surrounds bacterial cells, providing shape and protection against osmotic pressure.

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Peptidoglycan synthesis

The process by which bacteria synthesize peptidoglycan, involving the assembly of precursor molecules and their incorporation into the cell wall.

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NAM-NAG unit

A repeating disaccharide unit composed of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM), linked together by peptides to form the peptidoglycan mesh.

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What is a flagellum?

A rope-like structure that allows bacteria to move. It consists of a basal body, hook, and filament. The movement is driven by the rotation of the flagellum and is influenced by chemical stimuli (chemotaxis).

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What is flagellin?

A protein subunit that makes up the flagellum, responsible for the "H" antigen.

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What are fimbriae (pili)?

Tiny hair-like structures on the surface of bacteria, composed of pilin protein subunits. They're smaller than flagella, not coiled, and numerous. They help bacteria attach to surfaces and other bacteria.

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What is chemotaxis?

The process of bacteria moving in response to chemical stimuli, such as food or toxins. This is how they find nutrients and avoid harmful environments.

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What is a biocide?

A substance that kills bacteria or inhibits their growth, often used to remove biofilms.

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Study Notes

Microbiology Overview

  • Microbiology is the branch of knowledge dealing with microorganisms (microbes).
  • Microbes are organisms too small to see with the naked eye.
  • Key groups include viruses, bacteria, fungi, and parasites (protozoa).
  • Microbes vary in shape, size, appearance, genetic, and metabolic characteristics.

Microbial Sizes and Microscopes

  • Microbes are incredibly small, ranging in size from atoms to red blood cells.
  • Electron microscopes have a higher resolution power (0.25nm) than light microscopes (0.25µm).
  • Light microscopes use visible light and glass lenses.
  • Electron microscopes use electrons and electromagnets.

Comparing Light and Electron Microscopes

  • Light microscopes offer a magnification of x1500 and resolution of 250nm.
  • Electron microscopes offer a higher magnification of x500,000 and resolution of 0.25nm.
  • Light microscopes are generally cheaper and easier to use.

Microscope Parts

  • The light (optical) microscope consists of eyepiece, arm, rack stop, stage clip, coarse focus, fine focus, revolving nosepiece, objective lens, stage, condenser, illuminator, and base.

Viruses

  • Viruses are small (18-600 nm).
  • Viruses have subcellular structural organization and parasitize other organisms.

Bacteria

  • Bacteria are prokaryotic cells (no nucleus).
  • Bacteria lack intracellular compartmentalization.
  • Bacteria are smaller than eukaryotes (typically 1-10 µm).

Fungi

  • Fungi are eukaryotic cells.
  • Fungi have a nucleus and intracellular compartmentalization.
  • Fungi are larger than bacteria (yeasts are unicellular, molds are multicellular).

Protozoa

  • Protozoa are eukaryotic cells.
  • Protozoa have a nucleus and intracellular compartmentalization.
  • Protozoa are larger than bacteria (typically 1-100 μm.)
  • Many have complex life cycles involving biological vectors.

Eukaryotes vs Prokaryotes

  • Eukaryotes typically have a nucleus and other membrane-bound organelles.
  • Prokaryotes lack a nucleus and membrane-bound organelles.

Microbial Ubiquity

  • Microbes thrive in nearly every environment.
  • Microbes can withstand extremes in temperature, pH, and other conditions.

Microbial Impact on Human Health - Microbiota

  • Human microbiota are all microorganisms living in/on us.
  • Human microbiota are essential to function and health.
  • Microbiota found in the skin, gastrointestinal tract, vagina, oral cavity, and other systems.
  • Permanent and transient colonization by microbes/potential pathogens.

Microbial Impact on Human Health - Benefits

  • Food production (fermentation)
  • Clean-up of the environment
  • Agriculture (nitrogen, carbon, and sulfur conversion)

Microbial Impact on Human Health - Problems

  • Disruptions to the microbiota (gut dysbiosis) may cause digestive issues and increase the risk of certain diseases such as obesity, type 2 diabetes, cardiovascular disease, and infections.

Fecal Microbiota Transplantation (FMT)

  • A therapeutic intervention involving the transfer of fecal microbiota from a healthy donor to a recipient with dysbiotic gut microbiota.
  • FMT aims to restore diversity and function, improving gastrointestinal and non-gastrointestinal symptoms.
  • The samples undergo a process of homogenization, filtering, and encapsulation before being stored and used for transfer.

The Skin Microbiota

  • The skin microbiota is a significant part of the human microbiome in mass.
  • Microbial communities on the skin stabilize during puberty and post-puberty.

Bacterial Cell Walls

  • Gram-positive bacteria have a thick peptidoglycan layer.
  • Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane containing lipopolysaccharide.
  • Peptidoglycan synthesis uses many enzymes that synthesize and attach UDP molecules.
  • Mycolic acids (lipids in some bacteria) render some bacteria acid-fast.

Gram Staining

  • A rapid test that distinguishes between Gram-positive and Gram-negative bacteria.
  • Involves staining with crystal violet, iodine, a decolorizer, and safranin.
  • Based on differences in cell wall structure.

Bacterial Shapes and Arrangements

  • Bacteria can occur in various shapes (cocci, bacilli, spirals) and arrangements (chains, clusters, tetrads, sarcina).

Flagella and Fimbriae

  • Flagella are protein structures that facilitate bacterial movement.
  • Fimbriae are hair-like protein appendages aiding in adherence to surfaces (bacteria or host).

Biofilms

  • Communities of microorganisms encased in a self-produced extracellular polymeric substance.
  • Biofilms protect bacteria from the external environment and make them resistant to antibacterial interventions.
  • Biofilms cause significant problems in industrial processing and in human health.

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Description

Test your knowledge on the differences between Gram positive and Gram negative bacteria, focusing on peptidoglycan structure and related components. This quiz covers essential processes like NAG to NAM conversion and the roles of structures such as fimbriae and flagella in bacterial movement.

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