BACTERIAL CELL COMPONENTS

CELL WALL

↪ also referred to as the

↪ This structure gives the bacterial cell shape and strength to withstand changes in environmental osmotic pressures that would otherwise result in cell lysis.

↪ protects against mechanical disruption of the cell

↪ offers some barriers to the passage of larger substances.

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GRAM POSITIVE CELL WALL

↪ Has a very thick protective peptidoglycan (murein) layer

↪ Teichoic acid and lipoteichoic acid

GRAM NEGATIVE CELL WALL

↪ Thin peptidoglycan layer

↪ Outer membrane: proteins, phospholipids, and lipopolysaccharide (LPS).

↪ Functions of the Outer Membrane

1\. It acts as a barrier to hydrophobic compounds and harmful substances.

2\. It acts as a sieve, allowing water-soluble molecules to enter through protein-lined channels called porins.

3\. It provides attachment sites that enhance attachment to host cells.

GRAM VARIABILITY

↪ a characteristic exhibited by gram positive bacteria

↪ Natural gram variability: Mobiluncus spp. and Gardnerella vaginalis

↪ Acquired gram variability (for gram positive bacteria)

↪ Contributing factors

✧ Use of old culture

✧ pH of staining reagents

✧ bacterial autolysis

✧ Staining reaction time

(Gram Staining)

Primary stain ⎼ Crystal Violet

G(+) G(⎼)

(Purple) (Purple)

Mordanting ⎼ Gram’s Iodin

G(+) G(⎼)

(Purple) (Purple)

Decolorization ⎼ Acetone/Alcohol

G(+) G(⎼)

(Purple) (Colorless)

Secondary staining/Counterstaining ⎼ Safranin red

G(+) G(⎼)

(Purple) (Red/pink)

(NAG)

N-acetylglucosamine

(NAM)

N-acetylmuramic acid

(GRAM STAIN REACTION OF MEDICALLY IMPORTANT BACTERIA )

All COCCI are Gram POSITIVE except:

Neisseria, Branhameila/Moraxella, Veillonella

(GRAM STAIN REACTION OF MEDICALLY IMPORTANT BACTERIA )

All BACILLI are Gram NEGATIVE except:

Mycobacterium, Bacillus, Clostridium, Corynebacterium, Lactobacillus, Listeria, Erysipelothrix, Aerobic Actinomyces, Rothia, Kurthia (MBCCLLEARK)

Mycoplasma & Ureaplasma

have a gram negative reaction NOT because it has a gram negative cell wall but because they DO NOT HAVE a CELL WALL.

Spirals

are very difficult to stain using gram staining however stainable spirals are usually gram negative

Mycobacterium, Nocardia spp.

have a gram positive cell wall structure however because 60% of the cell wall is made of hydrophobic lipids mainly mycolic acid, it affects its permeability this makes it difficult to gram stain.

ACID-FAST CELL WALL

contain a waxy layer of glycolipids and fatty acids (mycolic acids) - *very hard to decolorize*

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ACID-FAST STAINING

specifically designed for a subset of bacteria whose cell walls contain long-chain fatty (mycolic) acids.

Mycolic acids

render the cells resistant to decolorization, even with acid alcohol decolorizers.

Mycobacteria

are the most commonly encountered acid-fast bacteria

Mycobacterium tuberculosis

the etiologic agent of tuberculosis.

(Acid Fast Staining)

Partially Acid Fast Organism

✧ Nocardia

✧ Rhodococcus

✧ Legionella micdadei

(Acid Fast Staining)

Distinctly Acid Fast

✧ Cryptosporidium

✧ Isospora

(Acid Fast Staining)

2 methods

✧ Ziehl-Neelsen Method (hot)

✧ Kinyoun Method (cold) - tergitol

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KINYOUN ACID-FAST METHOD

↪ does not require the use of heat or boiling water, minimizing safety concerns during the procedure.

↪ Because of a higher concentration of phenol in the primary stain solution, heat is not required for the intracellular penetration of carbol fuchsin.

↪ referred to as the “cold staining” method

(Ziehl-Neelsen Method)

Acid Alcohol

3%HCI in 95% Ethanol

Kinyoun Method

3% H2SO4 in 95%Ethanol

**(PARTS INTERNAL TO THE CELL WALL)**

CYTOPLASMIC/PLASMA MEMBRANE

a phospholipid bilayer embedded with proteins that envelops the cytoplasm but does not contain sterols (except Mycoplasma/Ureaplasma)

**Acts as an osmotic barrier**

**Site of electron chain transport**

**(PARTS INTERNAL TO THE CELL WALL)**

MESOSOMES

↪ folds or invagination along the length of the cytoplasmic/plasma membrane which serves as a point of attachment for chromosomes

**(PARTS INTERNAL TO THE CELL WALL)**

FREE RIBOSOMES

↪ sites of protein synthesis in bacterial cells which has a size of 70S comprised of two subunits being 50S and 30S.

**(PARTS INTERNAL TO THE CELL WALL)**

INCLUSION BODIES

↪ serves as depot or storage deposits under certain circumstances such as limited or excess of a particular nutrient.

**(PARTS INTERNAL TO THE CELL WALL)**

MUCH GRANULES

contains lipids (Mycobacterium tuberculosis)

**(PARTS INTERNAL TO THE CELL WALL)**

VOLUTIN/BABES-ERNST BODIES/METACHROMATIC GRANULES

contains polyphosphates or inorganic phosphates (Corynebacterium diphtheriae)

**(PARTS INTERNAL TO THE CELL WALL)**

BIPOLAR BODIES

prominent staining of each end of the bacilli Yersinia pestis using Methylene Blue or WAYSON stain giving it a “**safety pin appearance”**

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**(PARTS INTERNAL TO THE CELL WALL)**

BACTERIAL SPORES/ENDOSPORES

**↪ complex multilayered highly refractile structure that can be found within**

(PARTS EXTERNAL TO THE CELL WALL)

PILI or PILUS

protein projections that are thinner and shorter than flagella and are most usually found in gram negative bacteria.

(PARTS EXTERNAL TO THE CELL WALL)

The Term Fimbriae in **Latin**

Fringe

(PARTS EXTERNAL TO THE CELL WALL)

The Term PILI in **Latin**

Hairs

(PARTS EXTERNAL TO THE CELL WALL)

Common/Somatic/Ordinary (Pili)

usually shorter, numerous, sticky hair-like appendages that are primarily used for adherence to one another, host cells, and environment surfaces.

(PARTS EXTERNAL TO THE CELL WALL)

Sex/Fertility/Pilus

usually longer and singular, long and hollow protein tubes that is primarily used for bacterial conjugation.

The Two important Sporulating Bacteria

Bacillus and Clostridium

(PARTS EXTERNAL TO THE CELL WALL)

Flagella Or Flagellum

\- (for movement) (longer than pili)

exterior protein filaments or whip-like projections which is embedded in the cell envelope with a motor attached in a basal body responsible for its propeller-like rotation of the ________ which makes bacteria move.

(PARTS EXTERNAL TO THE CELL WALL)

GLYCOCALYX

\-polysaccharide

exterior high molecular weight appendage or structure usually made up of polysaccharide polymers or sometimes polypeptides which are produced by certain bacteria depending on environmental and growth conditions surrounding the bacterial cell.

(PARTS EXTERNAL TO THE CELL WALL)

2 Forms of GLYCOCALYX

Capsule and K Antigen (Kapsule)

(PARTS EXTERNAL TO THE CELL WALL)

CAPSULE

* uniform and condensed organized material that is firmly attached to the cell wall of the bacteria

(PARTS EXTERNAL TO THE CELL WALL)

K Antigen (Kapsule)

a slight change in the capsular

MEDICALLY IMPORTANT CAPSULATED BACTERIA

Neisseria meningitidis

Haemophilus influenzae serotype b

Streptococcus pneumoniae

Klebsiella pneumoniae

Bacillus anthracis

(PARTS EXTERNAL TO THE CELL WALL)

SLIME LAYER

* unorganized (acts as phagocytosis)
* loose or diffused, thick, viscous unorganized material that appears to be detached
* primarily it also serves as a form of protection from phagocytosis, or in some instances, it helps the bacteria to adhere to host tissues or synthetic implants such as prosthetic heart valves.