Cariology Exam One [Introduction to Microbiology: Banas]

Eukaryotic Microbes:

- Fungi (molds and yeast)

- Parasites and worms

Eukaryotic microbes are

Single-celled or Multicellular

Prokaryotic Microbes:

Bacteria

Prokaryotic Microbes are:

Single-celled but may exist in chains or groups

Acellular Microbes

Viruses

Acellular Microbes are

Nucleic acid surrounded by proteins

Microbes differ vastly in

Size

Typical brightfield microscope will have a ___x eyepiece and objective of ___,___,___

10x eyepiece

10x,40x,100x objectives

Brightfield microscope: Low power

100X magnification

Brightfield microscope: High-dry power

400x

Brightfield microscope: Oil immersion

1000X

Brightfield microscope: Magnification suitable for viewing eukaryotic cells

Low and high-dry

To satisfactorily assess bacterial morphology, viewing under __________ is necessary

oil immersion (1000X magnification)

Electron microscopy in its various forms has suitable resolving power in a range from

5000x to 1,000,000x

To see the structure of viruses requires magnification of approximately

> 20,000x

The microflora of the oral cavity can include

Yeasts, bacteria, and viruses

The primary inhabitants of dental plaque and causative agents of dental caries are

Bacterial species

Classification of Bacteria (that we need)

Gram Negative

Gram Positive

Cell wall-less

Archaebacteria

Eukaryotic versus Prokaryotic: Eukaryotic

- Generally > 5μm

- Has a nucleus and other internal membrane-bound compartments

- DNA in diploid genome

- No cell wall except fungi

- Cytoplasmic membranes contains sterols

- 80S ribosomes (60S + 40S)

- mRNA must exit nucleus to be translated

- Respiration in mitochondria

- Sexual or asexual reproduction

Eukaryotic versus Prokaryotic: Prokaryote

- Generally 0.5-3.0μm

- No nucleus and no internal membrane-bound compartments

- Single, circular haploid genome

- Usually a peptidoglycan cell wall

- No sterols

- 70S ribosomes (50S + 30S)

- Transcription and translation occur together

- Respiration in plasma membrane

- Asexual reproduction

Bacteria can be visualized without stain by using

phase contrast or darkfield light microscopy

Bacteria are more commonly stained using a simple stain or the differential stain called the _____ and visualized by brightfield microscopy

Gram stain

Gram staining: Gram Positive

1. Fixation

2. Crystal violet (Dark purple)

3. Iodine treatment (Light purple)

4. Decolorization (Does not effect: Light purple still)

5. Counter stain (does not effect)

Purple stained

Gram staining: Gram Negative

1. Fixation

2. Crystal violet (Dark purple)

3. Iodine treatment (Light purple)

4. Decolorization (Colorless)

5. Counter stain (Pink)

Pink stained

Bacterial Shapes

Cocci

Rods

What corresponds to the Gram reaction

Cell wall anatomy

Peptidoglycan

Repeating disaccharides; the amino acid crosslink is always attached to the N-acetylmuramic acid moiety

Cross-linking is

the connection between amino acid side chains.

This connection is often direct in Gram-Negative, but via a penta-glycine bridge in Gram-Positive

What type of bacteria are more extensively cross-linked

Gram Positive

Different Structures between gram + and gram - membrane

Gram +

- Has a thicker peptidoglycan layer

- Teichoic acids

- Lipoteichoic acids

Gram -

- Has a thinner peptidoglycan layer

- Lipopolysaccharides

Lipopolysaccharide (LPS)

- Endotoxin

- Component of almost all Gram-Negative

- Only acts as endotoxin when released from lysed bacterial cells

- Lipid A portion is the most toxic

- Can be responsible for septic shock

- Endotoxin from different species possesses different toxic potential

Lipopolysaccharide structure

- Lipid A portion

- Inner and outer core glycolipid

- O antigen (specific subunit)

QUESTION: Which of the following allows direct access to extracellular substances that attach the peptidoglycan component of the cell wall?

1. Gram Positive

2. Gram Negative

1. Gram positive

- Don't have to go through an outer membrane in order to get to the peptidoglycan

It is impossible to avoid bacteria we must

coexist

We have evolved an association with

bacteria in our environment

In most instances the association with bacteria is

commensal or mutualistic

A normal flora

Stimulates and strengthens our immune system, synthesizes certain vitamins, and helps reduce the opportunities for colonization with pathogenic species

Who lives where: Skin

- Mostly Gram +

- difference between dry and moist areas

Who lives where: Oral

- Mix of Gram + species

- Differences based on distinct niches

Who lives where: Urigenital

- Mostly skin organisms but can be acidogenic species like lactobacilli

Who lives where: Digestive tract

- Mostly Gram - anaerobes

- spares in stomach and small intestine

- Colon heavily populated

BACTERIAL PROPERTY: Adhesion

HOST RESPONSE:

- Mechanical

-- barriers, swallowing, peristalsis, coughing, flow of urine, cell sloughing, oral hygiene

-Innate immunity

-- Lysozyme, pH, Phagocytosis

- Adaptive immunity

-- Ig, cT Cells

BACTERIAL PROPERTY: Invasion, phase variation

HOST RESPONSE:

- Adaptive immunity

BACTERIAL PROPERTY: Toxins (endotoxins, exotoxins)

HOST RESPONSE:

Adaptive immunity (keep bacterial population low)

BACTERIAL PROPERTY: Degradative enzymes

HOST RESPONSE:

Adaptive immunity (keep bacterial population low)

BACTERIAL PROPERTY: Metabolic byproducts (acid)

HOST RESPONSE:

- keep bacterial population low

- Buffering by saliva

Bacteria that can cause disease are called

Pathogens

The pathogen establishes an infection leading to

symptoms of disease

Properties of bacteria that make the host sick are called

virulence factors

Disease symptoms in the host often contribute to

dissemination of the pathogen

Other times disease can result from overgrowth of

particular normal microflora species, or if the normal flora can be introduced into normally sterile sites

- Opportunistic infection

Dental caries and periodontal disease are generally considered

opportunistic infections that result from changes in the ecology of the oral microflora

The altered composition of the microbiome in the oral cavity by opportunistic bacteria is said to be in

dysbiosis

Endodontic infections might be considered an example of the

oral microflora contaminating a normally sterile site

SUMMARY: Bacteria are classified as prokaryotes, have variety of shapes, and can usually be classified as either

Gram positive or Gram negative

SUMMARY: The Gram reaction is based upon differences in the cell wall which in turn plays a role in

where the organism can best survive and which influences clinical care

SUMMARY: We have a normal microflora that is particularly rich in

the oral cavity

SUMMARY:

Bacteria have a variety of means for

The host has several means

Bacteria:

Colonizing and propagating

Host:

Designed to limit bacterial population