Microbiology Chapter on Gram Negative Bacteria

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Questions and Answers

What is the primary function of the periplasmic space in Gram negative bacteria?

It stores genetic material.

It serves as a barrier against antibiotics.

It contains transport systems for essential molecules. (correct)

It is involved in bacterial respiration.

Which of the following hydrolytic enzymes is NOT mentioned as being present in the periplasmic space?

Proteases

Lipases

Nucleases

Amylases (correct)

What role do collagenases and hyaluronidases play in bacterial infection?

They aid in the degradation of host tissues. (correct)

They enhance the bacteria's resistance to antibiotics.

They inhibit bacterial growth.

They stimulate immune response.

Which component of lipopolysaccharide (LPS) is responsible for its endotoxin activity?

Lipid A (B) Signup and view all the answers

How does the structure of Lipid A contribute to its function?

Its fatty acids allow it to anchor in the outer membrane. (A) Signup and view all the answers

What is the primary component of the cell wall in Gram positive bacteria?

Peptidoglycan (B) Signup and view all the answers

What characteristic distinguishes Gram negative bacteria from Gram positive bacteria?

Thinner peptidoglycan layer (B) Signup and view all the answers

Which of the following is NOT a characteristic of Mycobacteria's cell wall?

Presence of a thick peptidoglycan layer (A) Signup and view all the answers

What role does crystal violet play in the Gram staining process?

It is the primary dye that stains Gram positive bacteria purple (C) Signup and view all the answers

Which structure in Gram negative bacteria allows them to resist the crystal violet during Gram staining?

Outer membrane (A) Signup and view all the answers

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

To restore gut microbial diversity and function (A) Signup and view all the answers

How is the skin microbiota primarily organized in terms of microbial mass?

It is the second largest in mass after gut microbiota (B) Signup and view all the answers

Which of the following is NOT a function of the skin microbiota?

Enhancing pathogen growth (C) Signup and view all the answers

What environmental factors can disrupt the skin microbiota?

Cosmetic products and poor diet (D) Signup and view all the answers

Which structure is NOT typically found in bacteria?

Nucleus (C) Signup and view all the answers

What is a distinctive feature of bacterial DNA compared to eukaryotic DNA?

It is circular and haploid (B) Signup and view all the answers

What role do topoisomerases play in bacterial DNA architecture?

They support topological changes in DNA architecture (C) Signup and view all the answers

Which characteristic describes plasmids in bacteria?

They are extrachromosomal and circular (D) Signup and view all the answers

What structural characteristic distinguishes Gram positive bacteria from Gram negative bacteria?

Thick, multilayered cell wall with at least 40 layers of peptidoglycan (A) Signup and view all the answers

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

Lysine or Diaminopimelic Acid (D) Signup and view all the answers

What occurs during the biosynthesis of peptidoglycan inside the bacterial cell?

NAG is converted into NAM and activated with UTP to form UDP-NAM (C) Signup and view all the answers

What is the primary function of the bacterial cell wall?

To provide resistance to osmotic pressure and protect from environmental threats (A) Signup and view all the answers

Which feature accurately describes the peptidoglycan structure?

It is a rigid mesh of linear polysaccharide chains cross-linked by peptides (A) Signup and view all the answers

What is the primary function of transglycosylases in peptidoglycan synthesis?

To attach the disaccharide building block to the existing peptidoglycan chain (C) Signup and view all the answers

What role does bactoprenol play in the synthesis of peptidoglycan?

It acts as a carrier for UDP-NAM pentapeptide to the outside of the cell (C) Signup and view all the answers

Which enzymes are classified as penicillin-binding proteins (PBPs)?

Both transpeptidases and carboxypeptidases (A) Signup and view all the answers

What occurs to the disaccharide building block after its attachment to the peptidoglycan chain?

It is cross-linked to adjacent glycan chains (B) Signup and view all the answers

What is the purpose of carboxypeptidases in peptidoglycan synthesis?

To remove terminal D-Ala and regulate cross-linking (B) Signup and view all the answers

What process primarily allows nitrogen, carbon, and sulfur to be converted into usable forms for plant growth?

Sustaining agriculture (A) Signup and view all the answers

What refers to the microorganisms living in and on the human body?

Microbiota (B) Signup and view all the answers

What is a key difference between permanent and transient microbial colonization?

Transient colonization involves pathogens. (C) Signup and view all the answers

During which stage does the intestinal microbiota become similar in diversity and stability to that of adults?

Toddler years (D) Signup and view all the answers

Which of the following is NOT a function of the intestinal microbiota?

Regulation of genetic material (B) Signup and view all the answers

What type of intervention does fecal microbiota transplantation (FMT) represent?

Therapeutic intervention (A) Signup and view all the answers

How might differences in infant feeding impact the intestinal microbiota?

By determining the types of microbes and their diversity. (D) Signup and view all the answers

What percentage of the total gut microbes are fungi?

0.1% (A) Signup and view all the answers

Study Notes

Microbiology Overview

Microbiology is the study of microorganisms, organisms too small to be seen with the naked eye.
Major groups include viruses, bacteria, fungi, and parasites (protozoa).
Microbes vary in shape, size, and genetic and metabolic characteristics.

Microbial Size and Microscopy

Microbes are very small, ranging from atoms to cells.
Electron microscopes have a higher resolution than light microscopes.
Electron microscopes can magnify objects thousands of times more than light microscopes.

Comparing Light and Electron Microscopes

Light microscopes use visible light.
Electron microscopes use electrons.
Light microscopes magnify images up to 1500x.
Electron microscopes magnify images up to 500,000x.
Light microscopes use glass lenses.
Electron microscopes use electromagnets.
Light microscopes can view living and non-living things.
Electron microscopes can mainly view non-living things.
Light microscopes are cheap.
Electron microscopes are expensive.
Light microscopes are portable.
Electron microscopes are static.

Microscopy Overview

The light microscope uses visible light and a system of lenses to produce magnified images of small objects.
The parts of a microscope include the eyepiece, arm, rack stop, stage clip, coarse focus, fine focus, revolving nosepiece, objective lens, stage, condenser, illuminator, and base.
Gram positive and negative bacteria can be visually distinguished via a staining procedure when using a light microscope.

Viruses

Small size (18-600 nm)
Subcellular structural organization.
True parasites.

Bacteria

Prokaryotic cells.
Lack a nucleus.
Lack intracellular compartments.
Typically smaller than eukaryotes (1-10 μm).
Possess various structural components: capsule, fimbriae, ribosomes, pili, slime, mesosome, cytoplasm, flagella, membrane, plasmid, cell wall, and nucleoid.

Fungi

Eukaryotic cells.
Contain a nucleus and have intracellular compartments.
Larger than bacteria.
Yeasts (unicellular) are typically 15-10 μm.
Moulds (multicellular) can reach up to 50 μm.

Protozoa

Eukaryotic cells.
Nucleus and intracellular compartmentalization.
Some exhibit motility via pseudopods, flagella, or cilia.
Larger than bacteria (typically up to 100 μm).
Complex life cycles often involving biological vectors.

Eukaryotes and Prokaryotes

Key differences in size, nuclear structures (nucleus presence), chromosomes (number and structure), and cytoplasmic structures (e.g., mitochondria).
Eukaryotic ribosomes are 80S, and prokaryotic ribosomes are 70S.

Microbial Distribution

Microbes are ubiquitous; they live almost everywhere on Earth (in various environments, including high/low temperatures, acidic/alkaline conditions, and high pressure).
Microbes can live in nearly any kind of environment.

Microbial Impact on the Environment

Critical role in sustainability (conversion of nitrogen, carbon, and sulfur into usable forms for plants).
Useful in cleaning up some environmental pollutants.

Microbial Impact on Human Health

Essential for food production (fermentation).
Important participants in the human microbiota (skin, oral, vaginal, and gastrointestinal tracts).
Roles in human health and disease.
Colonization begins at birth. It's of two types: permanent or transient colonization.

Microbial Impacts on the Human Body

Different types of microbes live on/in different parts of the body.
Human microbiota affects health by maintaining balance.
Imbalances in the microbiota can lead to various health issues.

Fecal Microbiota Transplantation

Fecal microbiota transplantation (FMT) involves transferring fecal microbiota from a healthy donor to a recipient with a disrupted gut microbiota.
FMT is thought to work by restoring gut microbial diversity and function.

The Intestine Microbiota

Microbes that live on/in the different parts of the intestinal tract vary greatly.
The intestinal microbiota affects human health.
The intestinal microbiota and its diversity change from infancy to adulthood.

The Skin Microbiota

Second-largest microbiota in the human body.
Made up of 10^8 – 10^10 microbes per square cm of skin.
Restructured during puberty.
Microbial communities stabilize after puberty.

Disruption of Microbial Balance

Imbalance in the skin microbiota can cause issues like acne.
Other microbial imbalances can cause various health conditions.

Importance of Gram and Ziehl-Neelsen Stains

Both techniques identify bacteria based on their cell wall structure.
Gram stain differentiates Gram-positive and Gram-negative bacteria.
Ziehl-Neelsen stain identifies acid-fast bacteria.

Bacterial Cell Wall Structure

Gram-positive bacteria have a thick cell wall composed of peptidoglycan.
Gram-negative bacteria have a thin cell wall with an additional outer membrane. The outer membrane contains lipopolysaccharide (LPS).

Bacterial Cell Wall Components

Peptidoglycan (or murein), a major component of bacterial cell walls.
Teichoic and lipoteichoic acids strengthen the cell wall in Gram-positive bacteria.
Lipopolysaccharide (LPS) is a major component in Gram-negative bacterial cell walls.

Bacterial External Structures: Capsules, Flagella, Fimbriae

Capsules are protective polysaccharide layers that enhance microbial survival and biofilm formation.
Flagella are whip-like appendages for motility.
Fimbriae are hair-like appendages that aid in attachment to surfaces.

Biofilms

Biofilms are well-organized communities of microbes encased in a self-produced extracellular matrix.
Biofilms can cause problems in industrial processing equipment.

Bacterial Shapes and Arrangements

Common bacterial shapes include coccus (spherical), bacillus (rod-shaped), spiral.
Bacterial arrangements can include diplococci, streptococci, staphylococci, tetrads, and sarcinae.

Bacterial Structures: DNA Chromosome and Plasmids

Bacterial DNA chromosome is single, circular, and supercoiled.
Plasmids are extrachromosomal circular DNA molecules.

Bacterial Structures: Cytoplasmic Structures:

Cytoplasmic membrane is a lipid bilayer that encloses the cytoplasm. Other cytoplasmic structures are ribosomes, involved in protein synthesis, an important location for various key cellular activities.

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Description

Test your knowledge on the unique characteristics and functions of Gram negative bacteria in this informative quiz. Explore key topics like periplasmic space, hydrolytic enzymes, and the Gram staining process. Perfect for microbiology students and enthusiasts!