Unit 2. General Characteristics of Bacteria

Bacteria

• unicellular organisms that lack a nuclear membrane and true nucleus

• prokaryotes

• having no mitochondria, endoplasmic reticulum (ER), or Golgi bodies (they only have ribosomes)

Bacterial cell wall

______________ differences provide the basis for the Gram stain

capsule

• structure that helps evade phagocytosis

• obscure antigenic material

• variable (may or may not be present)

Gram staining

a test to initially identify bacteria into 2 major groups:

A. Gram positive

B. Gram negative

0 .25-1 μm in width

1-3 μm in length

BACTERIAL SIZE:

• Most clinically relevant bacterial species range in size

T

• virus = nanometer (10^-9) = electron microscope

• bacteria = micrometer (10^-6) micrometer = brightfield microscope

T or F

Virus is smaller than bacteria.

asymmetric growth of the cell wall

Variation of size and shape within a population may also result from ________________________

Haemophilus ducreyi

• smallest bacteria

• causes chancroid

Bacillus anthracis

• largest bacteria

• causes anthrax

1. cocci

2. bacillus

3. coccobacilli

4. fusiform

5. curved

6. spirochette

7. pleomorphic

BACTERIAL SHAPE (7)

[NoBoyVrend] nega mga ekalal

• Neisseria spp.

• Branhamella spp.

• Veillonella spp.

BACTERIAL SHAPE

• all cocci shaped bacteria are Gram positive, except for the 3

bacillus

BACTERIAL SHAPE

• rod shaped

• Bacillus anthracis

• Enterobacteriaceae

  • Escherichia coli

  • Shigella spp.

bacillus examples

Coccobacilli

• Gardnerella spp. (normal flora in female vagina)

BACTERIAL SHAPE

• ovoid

fusiform

BACTERIAL SHAPE

• tapered ends

Vibrio cholerae

curved bacteria example

spirochettes

BACTERIAL SHAPE

• flexous helical coil

• darkfield microscopy

• Leptospira interrogans - leptospirosis

• Borrelia burgdorferi - lime disease

• Treponema pallidum - syphilis

[LowBaT nako kaya paikot ikot ako na lang]

spirochettes example

Pleomorphic

BACTERIAL SHAPE

• no defined shape

• because of their cell envelope

• Mycoplasma spp.

• Ureaplasma spp.

ALL bacteria have cell wall, except for this 2

1. Staph - clusters

2. Strep - chains

3. Diplo - pairs

4. Tetrads

5. Packets of 8

6. Palisadin - picket-fence arrangement

7. Chinese characters

BACTERIAL ARRANGEMENT (7)

1. Staph - Staphylococcus

2. Strep - Streptococcus

3. Diplo - Neisseria gonorrhoeae, Streptococcus pneumoniae

4. Tetrads - Micrococcus, Pediococcus

5. Packets of 8 - Sarcina

6. Palisadin - picket-fence arrangement

7. Chinese characters - Corynebacterium diphtheriae

BACTERIAL ARRANGEMENT (7) & THEIR EXAMPLES

Streptococcus pneumoniae

Gram positive diplococci

Neisseria gonorrhoeae

Gram negative diplococci

[POCC]

1. Outer membrane

2. Cell wall

3. Periplasm

4. Cytoplasmic/cell membrane

CELL ENVELOPE COMPOSITION (4)

OUTER MEMBRANE

CELL ENVELOPE COMPOSITION

• Function as cell’s initial barrier to the environment

• primary permeability barriers to hydrophilic and hydrophobic compounds

• contain essential enzymes and other proteins located in the periplasmic space

• Bilayered structure

• Plays a significant role in the ability of certain bacteria to cause disease (virulence)

gram-negative bacteria

CELL ENVELOPE COMPOSITION

• outer membrane is found only on

• lipopolysaccharide

• net negative charge

CELL ENVELOPE COMPOSITION

• Outer membrane is composed of _____________ Which gives the surface of gram-negative bacteria a ______________

• porins

• murein lipoproteins

Structures found in the outer membrane

PORINS

Structures found in the outer membrane

• Protein structures scattered throughout the lipopolysaccharide macromolecules

• Water-filled structures that control the passage of nutrients and other solutes, including antibiotics, through the outer membrane

• Influence the extent to which various substances pass through the outer membranes of different bacteria

MUREIN LIPOPROTEINS

Structures found in the outer membrane

• Facilitate the attachment of the outer membrane to the next internal layer in the cell envelope, the cell wall

• bridge between outer membrane & inner structure

Cell wall / Murein Layer / Peptidoglycan

CELL ENVELOPE COMPOSITION

• 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 and offers some barrier to the passage of larger substances

Cell wall

CELL ENVELOPE COMPOSITION

• the part that is stained in Gram staining

Disaccharide-pentapeptide subunits

CELL ENVELOPE COMPOSITION

• cell wall is composed of

N-acetyl-D-glucosamine (NAG)

N-acetyl-D-muramic acid (NAM)

Structures in the cell wall

• Alternating sugar components (moieties),with the amino acid chain linked to N-acetylmuramic acid molecules

• Layers of these sheets are cross-linked with one another, forming a multilayered, cross-linked structure of considerable strength

• peptide bridges

• peptidoglycan sheets

• Murein sacculus/ sack

Structures in the cell wall

• Polymers of NAM & NAG Polymers cross-link to one another by means of __________ to form ____________

• this is referred to as _________________, this peptidoglycan structure surrounds the entire cell

mycolic acid (glycolipid + fatty acid)

a waxy cell wall contains _______________ that gives the bacteria a weak or ghost stain

Acid-Fast Staining

Instead of gram staining, this is used for bacteria that have high amounts of mycolic acid in their cell wall

• Mycobacteria

• Nocardia

• Legionella micdadei

• Tsukamurella

• Gordonia

• Rhodococcus

[MNL ToGetheR]

bacteria that have mycolic acid and is best stained using AFS

carbol fuchsin

primary stain used in AFS

red stain

color of AFS positive result

Acid-fast bacilli

term used to call bacteria that are positive for AFS

Gram-positive cell wall

Gram + or -

• Composed of a very thick protective peptidoglycan (murein) layer

• Consists of glycan (polysaccharide) chains of alternating N-acetyl-d- glucosamine (NAG) and Nacetyl-d-muramic acid (NAM)

cephalosporins (e.g., penicillin)

antibiotics that are effective against gram-positive organisms act by preventing synthesis of peptidoglycan are called

most effective against gram-positive bacteria

cell wall

The appendages like flagellum and pili are anchored by ________, it provide also support for the flagella and pili of bacteria

• Teichoic acid

• Lipoteichoic acid

• Teichuronic acid

Structures in the GRAM POSITIVE cell wall

• enumerate the 3 acids

TEICHOIC ACID

Structures in the GRAM POSITIVE cell wall

• anchored to the peptidoglycan (N-acetylmuramic acid)

• glycerol or ribitol phosphate polymers combined with various sugars, amino acids, and amino sugars

LIPOTEICHOIC ACID

Structures in the GRAM POSITIVE cell wall

• anchored to the PM (plasma membrane)

• linked to the next underlying layer, PM or cellular memebrane

TEICHURONIC ACID

Structures in the GRAM POSITIVE cell wall

• similar polymers, but the repeat units include sugar acids (eg, N-acetylmannosuronic or d-glucosuronic acid) instead of phosphoric acids

• synthesized in place of teichoic acids when phosphate is limiting

• Outer membrane

• Inner peptidoglycan layer (cell wall)

Structures in the GRAM NEGATIVE cell wall

• composed of two layers:

• proteins

• phospholipids

• lipopolysaccharides (LPS)

[LipPPtolelat]

Outer membrane contains (3)

• O-specific polysaccharide

• Core polysaccharide

• Lipid A (endotoxin)

[LPS → GPS: LOC]

LPS THREE REGIONS:

O-specific polysaccharide

LPS THREE REGIONS:

• antigenic

• causes immune respone

• can be used for serotyping

Core polysaccharide

LPS THREE REGIONS:

• ketodeoxyoctanoic acid (KDO) and heptose

• for viability of bacteria

Lipid A

LPS THREE REGIONS:

• inner, major constituents

• released when bacteria lyses → activates T cells → activates other immune cells → procudes fever and shock hence, an ENDOTOXIN

• consists of phosphorylated glucosamine disaccharide units to which are attached a number of long-chain fatty acids

binary fission

mode of reproduction of bacteria

• spherical

• rod-shape

• filamentous

Gram positive bacteria shapes

• spherical

• oval

• straight or curved

• helical or filamentous

Gram positive bacteria shapes

chemoorganoheterotrophic

Gram positive bacteria metabolism

• Chemoorganoheterotrophic

• Chemolitoautotrophic

• Phototrophic

Gram negative bacteria metabolism

Present in some

• Clostridium spp.

• Bacillus spp.

Gram positive bacteria endospore

absent

Gram negative bacteria endospore

PERIPLASMIC SPACE

CELL ENVELOPE COMPOSITION

• Bounded by the internal surface of the outer membrane and the external surface of the cellular membrane encompassing the thin peptidoglycan layer

• Contains the murein layer, consists gellike matrix containing nutrient-binding proteins that assist in the capture of nutrients from the environment

PERIPLASMIC SPACE

CELL ENVELOPE COMPOSITION

• Contains several enzymes involved in the degradation of macromolecules and detoxification of environmental solutes, including antibiotics that enter through the outer membrane

gram-negative bacteria

periplasmic space is found only on

Acid-fast cell wall

• Have a gram-positive cell wall structure

• Contain a waxy layer of glycolipids and fatty acids (mycolic acid) bound to the exterior of the cell wall

• More than 60% of the cell wall is lipid

Mycolic Acid

• Major lipid component in acid-fast cell wall

• Strong “hydrophobic” molecule that forms a lipid shell around the organism and affects its permeability

• Makes Mycobacterium spp. difficult to stain with the Gram stain

CYTOPLASMIC/ CELL (INNER) MEMBRANE

CELL ENVELOPE COMPOSITION

• Present in both gram-negative and gram-positive bacteria

• deepest layer of the cell envelope

• Consist of phospholipid bilayer, various proteins (70%), including a number of enzymes vital to cellular metabolism

• Serves as an additional osmotic barrier

CYTOPLASMIC/ CELL (INNER) MEMBRANE

CELL ENVELOPE COMPOSITION

1. Ribosomes

2. Genome

3. Plasmid

4. Inclusion bodies

5. Endospores/Asexual Spores

[Ritz Gumabay cutiPIE]

CYTOPLASMIC STRUCTURES (5)

Ribosomes

CYTOPLASMIC STRUCTURES

• Site of protein biosynthesis and give the cytoplasm a granular structure

• RNA + proteins

70S size

• 50S subunit

• 30S subunit

CYTOPLASMIC STRUCTURES

• ribosome size & subunits

Streptomycin

Gentamicin

This antibiotic/s attach to the 30S subunit and interfere with protein synthesis

Erythromycin

Chloramphenicol

This antibiotic/s attach to the 50S subunit and interfere with protein synthesis

Genome

CYTOPLASMIC STRUCTURES

• codes for all bacterial cell processes

• Appears as diffused nucleoid or chromatin body that is attached to a mesosome (sac-like structure)

single, circular chromosome

CYTOPLASMIC STRUCTURES

• bacterial genome structure

Nucleoid

CYTOPLASMIC STRUCTURES

• Feulgen positive

• Consists of a single continuous circular molecule ranging in size from 0.58 to almost 10 million base pair

• Borrelia burgdorferi

• Streptomyces coelicolor

All bacteria have a single continuous circular nucleoid except

• Vibrio cholerae

• Brucella melitensis

Few bacteria have dissimilar chromosomes like

Plasmid

CYTOPLASMIC STRUCTURES

• Extrachromosomal, double-stranded element of DNA that is associated with virulence

• Not essential for bacterial growth so a bacterial cell may or may not contain this

• Sometimes disappears during cell division and it can make bacteria (mostly Gram-neg) pathogenic

antibiotic resistance and toxin production

CYTOPLASMIC STRUCTURES

• Plasmid in the cytoplasm serves as a site for the genes to code for ________________________________

• Large plasmid

• Small plasmid

2 kinds of plasmid

large plasmid

2 kinds of plasmid:

• responsible for the production of B-lactamase that provide resistance to B-lactam antibiotics (penicillin and oxacillin)

Small plasmid

2 kinds of plasmid:

• Resistant to tetracyclines and chloramphenicol

INCLUSION BODIES

CYTOPLASMIC STRUCTURES

• Serve as the energy source or food reserve of the bacteria or as a reservoir of structural building blocks

• Composed mainly of polysaccharides

• lessen osmotic pressure

• glycogen

• cyanophysin

• poly-Bhydroxybutyrate granules

• carboxysomes (cyanobacteria, nitrifying bacteria, and thiobacilli)

• gas vacuoles (cyanobacteria, halobacterium, and thiothrix)

• polyphosphate granules (volutin and metachromatic granules)

CYTOPLASMIC STRUCTURES

• example of inclusion bodies

1. glycogen

2. polyphosphate granules

Two common types of cytoplasmic granules

glucose

Two common types of cytoplasmic granules

• Two common types of cytoplasmic granules

Polyphosphate granule

Two common types of cytoplasmic granules

• Storage form of inorganic phosphates

• Source of phosphate for nucleic acid and phospholipid synthesis

• Babes-Ernst bodies = Corynebacterium diphtheriae

• Bipolar bodes = Yersinia pestis, Burkholderia pseudomallei, Aggregatibacter spp.

• Much granules = Mycobacterium tuberculosis

• Halberstaedter–Prowazek bodies = Chlamydia trachomatis

• Levinthal–Cole–Lillie bodies = Chlamydia psittaci

[HaLa BBM!]

Examples of inclusion bodies in bacteria

(PHB) Poly-B-Hydroxybutyric acid

INCLUSION BODIES

• Lipid like compound consisting of chains of B-hydroxybutyric acid units connected through ester linkages

• Produced when the source of nitrogen, sulfur, or phosphorous is limited and there is excess carbon on the medium

PHB & Glycogen

INCLUSION BODIES

• Carbon source when protein and nucleic acid synthesis are resumed

Sulfur Granules

INCLUSION BODIES

• Hydrogen sulfide and thiosulfate

Endospores/ Asexual spores

CYTOPLASMIC STRUCTURES

• Small, dormant structures located inside the bacterial cell

• Aid in the survival of bacteria against external conditions

• Produced within vegetative cells of some Gram-positive bacteria

• Responsible for perpetuation, but not multiplication

dipicolinic acid + calcium ions = calcium cipicolinate

CYTOPLASMIC STRUCTURES

• endospores are made of

• Bacillus

• Clostridium

Bacteria-producing endospores

• Terminal spore

• Subterminal spore

• Central spore

Types of Spores according to location (3)

• Terminal spore = Clostridium tetani

• Subterminal spore = Clostridium botulinum (canned good bacillus)

• Central spore = Bacillus anthracis

Types of Spores according to location and their examples

• top-head

• lollipop

• tennis-racket

Types of Spores according to location:

• terminal spore morphology/appearance

bamboo pole appearance

Types of Spores according to location:

• central spore morphology/appearance