M2: BACTERIAL MORPHOLOGY, GROWTH REQUIREMENTS, THE CELL, BACTERIA STRUCTURE

ASK:

A - Attitude (heart)
S - Skill (hands)
K - Knowledge (head)

Anatomy of a Nurse

Bacteria

- A member of a large group of unicellular microorganisms that have cell walls but lack organelles
- Can cause disease
- Metabolically active single-celled prokaryotic bacteria divide by binary fission

Bacteria Morphology

Size, shape, and morphological arrangement of various bacteria can be easily viewed with a compound light microscope

Average coccus - is about 1um in diameter
Average bacillus - is about 1um wide x 3um long
Mycoplasma, the smallest microbe

Bacteria Size

Binary Fission

Bacteria Reproduce by?

Binary Fission

bacteria divide; one cell splits in half to become two daughter cells

Cocci - spherical
Bacilli - rod shape
Spirilla - spiral shape

Bacteria Basic Shapes

1. Diplococci
2. Streptococci
3. Staphylococci
4. Tetrad
5. Sarcina / Octad
6. Coccobacilli
7. Diplobacilli
8. Streptobacilli
9. Palisade
10. Vibrio
11. Spirochetes
12. Spirilla

Variety of Morphologic Arrangements

Diplococci

- singular: diplococcus
- cocci that divide and remain attached in pairs
- Examples: Streptococcus pneumonia, Moraxella catarrhalis, Enterococcus spp, Neisseria gonorrhea

Streptococci

- singular: streptobacillus
- rods that remain attached in chains after cell division
- Examples: Streptococcus pyogenes, Streptococcus pneumonia, Streptococcus mutans

Staphylococci

- singular: staphylococcus
- cocci in a grape like cluster or broadsheet
- Examples: Staphylococcus epidermidis, Staphylococcus haemolyticus, Staphylococcus aureus, Staphylococcus capitis

Tetrad

- a group of four cocci
- Examples: Aerococcus Pediococcus Tetragenococcus

Sarcina / Octad

- plural: sarcinae
- a group of eight bacteria that remain in a packet after dividing
- Examples: Sarcina aurantiaca, Sarcina lutea, Sarcina ventriculi

Coccobacilli

- plural: coccobacilli
- a bacterium that is an oval rod
- Examples: Chlamydia trachomatis, Haemophil

Diplobacilli

- singular: diplobacillus
- rods that divide and remain attached in pairs
- Examples: Coxiella burnetii, Klebsiella rhinoscleromatis, Moraxella bovis

Streptobacilli

- singular: streptobacillus)
- rods that remain attached in chains after cell division
- Examples: Streptobacillus moniliformis, Streptobacillus levaditi, Streptobacillus felis, Streptobacillus hongkongensis

Palisade

- picket fence-like shape due to a bend at the site of division during cell division;
- bacilli stack up next to each other, side by side
- Examples: Corynebacterium diphtheria that causes diphtheria

Vibrio

- these are the comma shaped bacteria that are slightly bent
- Examples: Vibrio mytili, Vibrio anguillarum, Vibrio parahaemolyticus, Vibrio cholera

Spirochetes

- are spiral bacteria that have a helical shape
- flexible & have an axial filament which helps in motility
- Examples: Leptospiraspecies (Leptospira interrogans), Treponema pallidum, Borrelia recurrentis

Spirilla

- helical shaped / corkscrew form
- have a similar structure with spirochete but more rigid
- like spirochetes, have a flagellum, but they lack the endo flagella
- Examples: Campylobacter jejuni, Helicobacter pylori, Spirillumwino gradskyi.

- Appendaged Bacteria
- Pleomorphic Bacteria
- Filamentous Bacteria
- Club-shaped Rod Bacteria

Other Shapes and Arrangements

Appendaged Bacteria

- bacteria that produce a distinct structure such as pillus or fimbriae. - those that produce these appendages are more virulent.
- Example: Neisseria gonorrheae, the agent of Gonorrhea.

Pleomorphic Bacteria

- this category includes bacteria that do not have a defined form.
- they can alter shape, but in pure culture, they appear to have a definite form
- Examples: Mycoplasma pneumoniae, M. genitalium.

Filamentous Bacteria

- this category includes bacteria that do not have a defined form.
- they can alter shape, but in pure culture, they appear to have a definite form
- Examples: Mycoplasma pneumoniae, M. genitalium.

Club-shaped Rod Bacteria

-these bacteria are thinner on one side than the other - Ex. Corynebacterium

1. Glycocalyx
2. Cell wall
3. Outer Membrane
4. Cell Membrane

Bacteria Envelope Structures

Glycocalyx

- The external surface of a plasma membrane that is important for cell-to-cell communication
- has capsule and slime layer

Capsule

A sticky layer that surrounds the cell walls of some bacteria, protecting the cell surface and sometimes helping to glue the cell to surfaces.

Slime layer

a glycocalyx that is unorganized and loosely attached to the cell wall

Cell wall

- also known as Murein Sacculus
- outermost component of all bacteria is the cell wall (except Mycoplasma species, which are bounded by a cell membrane, not a cell wall)
- principal component is -
-PEPTIDOGLYCAN (aka murein)
- provide rigidity strength, and protection
- has murein

murein

bacteria exoskeleton that completely surrounds the cell

Gram +
Gram -

Two Types of Gram

Gram positive

- thick layer / multi-layered
- has Teichoic acid and Polysaccharides

Teichoic acid

- responsible for flexibility of cell wall of the microorganisms
- a polysaccharide found in grampositive cell walls

Polysaccharides

- carbohydrate consisting of many sugar units; glycogen, cellulose, and starch are examples

Gram negative

- thin layered / monolayer
- surrounded by an outer membrane
- has presence of a plasma membrane located outside of the peptidoglycan layers, known as the outer membrane
- has lipoprotein, periplasmic space, acid-fast

Lipoprotein

-- large molecules known as lipopolysaccharide (LPS)
- anchored into the outer membrane and project from the cell into the environment

Periplasmic space

The space between the plasma membrane and outer membrane of Gram negative cell wall

Acid-fast

- outer-layer is lipid-rich; myolic acids (hydrophobic)
- inner layer is peptidoglycan

Outer Membrane

- Gram (-) bacteria's outer membrane
- made of LPS (LIPOPOLYSACCHARIDE)
- Has Lipid A and O polysaccharide

Cell Membrane

- other name cytoplasmic membrane
- located beneath the cell wall
- encloses the cytoplasm of cell
- cell sac or plasma membrane
- selective permeable
- property of a plasma membrane to allow certain molecules and ions to move through the membrane while restricting others

Antibiotic

Destroy the peptidoglycan or inhibit the synthesis of forming cell wall

Anti-fungal

Destroy the cell membrane

1. Flagella
2. Pili or Fimbriae
3. Axial filaments

Projecting Structures

Flagella

whiplike tails found in one-celled organisms to aid in movement

Taxis

- movement of a bacterium toward or away from a particular stimulus

Polar

- Molecule with partial charges. Mixes with water.
- at one or both ends of the cell

monotrichous

a single flagellum

lophotrichous

a tuft of flagella coming from one pole

amphitrichous

flagella at both poles of the cell

Peritrichous

having flagella distributed over the entire cell

Atrichous

bacteria that lack flagella

Pili or Fimbriae

function is adherence to cell surface

Fimbria

plural: fimbriae

an appendage on a bacterial cell used for attachment

Pilus

plural: pili

an appendage on bacterial cell; for Conjugation & gliding motility

Conjugation

transfer of genetic material from one cell to another involving cell-to-cell contact

Axial filaments

structure for motility found in spirochetes; also called endoflagellum

other name bundle of fibrils

function is motility

Cytoplasm (Cytoplasmic Membrane)

A jellylike fluid inside the cell in which the organelles are suspended

In a prokaryotic cell, everything is inside the plasma membrane

Nucleoiod
Mesosomes
Ribosomes
Granules
Endospores

Internal Structures of the Cytoplasm

Nucleoid

Region in a bacterial cell containing CHROMOSOMES

single circular, double-stranded DNA

Chromosomes

What does a nucleoid contain?

Mesosomes

an extension of the cell membrane that folds into the cytoplasm and increases surface area.

Serve in DNA replication and guide distribution of duplicated bacterial chromosomes into the two daughter cells during cell division

bacterial binary fission

process bacteria use to carry out cell division

(a) DNA Cycle that includes DNA replication and chromosome segregation

(b) Division Cycle that leads to cytokinesis and cell separation

Two segments of bacterial cell cycle

DNA CYCLE

includes DNA replication and chromosome segregation

DIVISION CYCLE

leads to cytokinesis and cell separation

Ribosomes

tiny spherical organelles that make proteins by joining amino together

function: protein synthesis

70S Proteins

all prokaryotes have 70S (where "S" = Svedberg units) ribosomes

composed of TWO SUB-UNITS:

50S

30S

Svedberg unit

offers a measure of particle size based on its rate of travel in a tube subjected on high G-force

Inclusion Bodies

Also referred to as "GRANULES"

a granule or viral particle in cytoplasm

or nucleus of some infected cells

Important in the identification of infectious viruses.

storage vessels of GLYCOGEN as a reserve for carbohydrates and energy

Main Function of Inclusion Bodies

Endosperes

resting structure formed inside SOME bacteria.

Allows bacterium to produce a dormant and highly resistant cell to preserve the cell's genetic material in times of extreme stress.

dipiclonic acid (DPA)

protects endospore genome from UV light.

plays roles in endospore heat resistance

Sporulation

aka "sporogenesis"

process of spore and endospore formulation

Vegetative State

normally-growing cell that forms the endospore

Germination

the process of beginning to grow from a spore to an endospore

(a) Endotoxins

(b) Exotoxins

Types of Toxins

Endotoxins

released only when bacteria die and their cell walls break down

activates host complement and coagulation cascades

causes septic shock

non-disease specific symptoms: fever, pain, shock, fatigue, discomfort

Exotoxins

produced and secreted

can result in severe disease-specific symptoms

ex: cholera, botulinum, diphtheria, tetanus toxin

(a) Enterotoxins
(b) Neurotoxins
(c) Cytotoxins

three main categories of extoxins

1. Carbon
2. Nitrogen, Sulfur, Phosphorous
3. Inorganic Ions
4. Growth Factors

Bacterial Growth Reuirements

Carbon

an essential element in building every macromolecule

Nitrogen

used in protein/amino acid synthesis and nucleic polymerization

Phosphorus

essential in nucleic acid synthesis and form of phospholipids

Sulfur

present in certain amino acids such as cysteine and methionine.

Inorganic Ions

small amounts of inorganic ions are required by all bacteria

Ex: Sulfur, phosphorus, potassium, magnesium, and calcium

Growth Factors

some bacteria cannot synthesize cell constituents

organisms can display wide variety of factor requirements

(a) Amino Acids

(b) Nucleotide Bases

(c) Enymatic Cofactors or "vitamins"

Typical Growth Factor Molecules

Vitamins

referred to as enzymatic cofactors

1. Moisure/Water
2. Oxygen
3. Temperature
4. pH
5. Osmotic Condition

Physical Requirements of Bacyeria

Moisture (water)

medium in which bacteria acquire nutrients

Oxygen

Include the following:

obligates aerobes - AEROPHILIC

obligate anaerobes

microaerophiles

facultative anaerobes

aerobes

Bacteria that require oxygen to grow

anaerobes

Bacteria that grow in the absence of oxygen and are destroyed by oxygen

Microaerophiles

require oxygen concentration lower than air

Aerobes that require Oxygen levels from 2-10% and have a limited ability to detoxify Hydrogen Peroxide and Superoxide Radicals

Facultative Anaerobes

can live with or without oxygen

Temperature

include the following:

mesophiles

pyschrotrophs

psychrophiles

hyperthermophiles

mesophiles

moderate temperature loving microbes

Psychrotrophs

microbes that have a maximum temperature for growth above 20 degrees C and are widespread in NATURAL environments and in foods.

causes food spoilage

Psychrophiles

have a maximum temperature for growth at 20 degrees C or below and are restricted to permanently COLD habitats.