Bacterial Cell and Its Ultra Structure Handouts

Bacterial Cell and its Ultrastructure

Mary Joyce Saborrido- Teoxon, RMT, MD, PCOM. PSMAP

What do we expect? Briefly describe the different microscopes used to identify

microbial agents Differentiate Prokaryotes vs. Eukaryotes Describe a Prokaryotic cell Identify the parts of a Prokaryotic cell Enumerate its function Differentiate a gram-positive and gram-negative bacteria

Microscope LIGHT ELECTRON

Microscope Confocal Scanning Laser Microscope

Microscope Scanning Probe Microscope

Important Microbial Groups Prions Viruses Bacteria

FungiParasites

Differentiate

Bacterial Morphology Shape , Arrangement

* Pleomorphic

Coccus / Cocci

Bacillus / Bacilli

Gram stain Composition: VIAS

Crystal Violet Gram’s Iodine Alcohol / Acetone Safranin

General Rules in Gram Staining

All cocci are Gram + EXCEPT:- Neisseria- Moraxella- Veillonella

All bacilli are Gram – EXCEPT:- Mycobacterium- Corynebacterium- Bacillus- Clostridium- Actinomyces- Streptomyces

Less common bacilli- Erysipelothrix- Listeria- Nocardia- -bacterium (Bifido-, Propioni-, Eu-, Arcano- )

What is the Gram’s reaction ?

Streptococcus Staphylococcus Neisseria Bacillus Escherichia

Bacterial Envelope (All the concentric surface layers of the bacterial cell)

Envelope Structure

Gram + or -

Chemical Composition

Function

Capsule-Slime-Glycocalyx

Both Gram+/ -

Polysaccharide gel

Pathogenicity/ Virulence factor;Protect againstPhagocytosis untilOpsonized; immunogenic

Envelope Structure

Gram + or -


Function

Outer membrane

“ major permeability

barrier”

Gram-negative

only

Phospholipid/ proteins:

Lipopolysaccharide

Lipid A

Polysaccharide

Hydrophobic

Membrane:

LPS= endotoxin

Lipid A=

Toxic moiety

PS= immunogenic


Outer Membrane

Envelope Structure

Gram + or -


Function

Gram + (thick)

Gram – (thin)

•Found in all free living bacteria EXCEPT

Mycoplasma

peptidoglycan; polymer of peptides (typically 4 amino acids long, cross-linked to other chains) and glycans (made of alternating amino sugars).

- Sugars found in peptidoglycan:

- N-acetylglucosamine (NAG).

- N-acetylmuramic acid (NAM).

Rigid support, cell shape, protection from osmotic damage Confer Gram reaction

Target of AB/ enzymes

Cell Wall =

Peptidoglycan

Cell wall

Cell Envelope Gram positive Gram negative

Envelope Structure

Gram + or -


Function

Cell Wall Acid-fast only

Mycolic acids Acid-fastness

Resistance to drying and chemicals

All organisms are non-acid fast EXCEPT:

Cryptosporidium sp.

Legionella micdadei

Isospora sp.

Mycobacterium sp

Nocardia sp.


Envelope Structure

Gram + or -


Function

Periplasmic space Gram-negative only

“Storage space” between the inner and outer membranes

Stores degradative enxymes which break down large molecules, (β-lactamases)

Aids regulation of osmolarity


Wall-less forms of Bacteria

Spheroplasts(+) OM

Protoplasts(-) OM

Envelope Structure

Gram + or -


Function

Cytoplasmic membrane

Both Phospholipid bilayer with many embedded proteins

Energy metabolism occurs here

Hydrophobic cell “sack”

Selective permeability and active transport

Envelope Structure

Gram + or -


Function

Pilus/ Fimbria

1. Common 2.Sex 3.Virulence

Primarily Gram -

Glycoprotein (pilin) Adherence to cell surfaces, including atachment to other bactera during conjugation

Envelope Structure

Gram + or -


Function

Flagellum

Axial Filaments

Both

Spirochetes

Protein (flagellin)

Protein

Motility

Motility

Internal Bacterial structure

Structure Gram + or -


Function

Nucleoid region

Also called neuclear body/ chromatin body/ nuclear region

Both DNA; RNA; Proteins Genetic material (all essential genes)

Internal Bacterial structureStructure Gram +

or -Chemical Composition

Function

Plasmids Both DNA Non-essential genetic material

Roles in conjugation, drug resistance, toxin production

Internal Bacterial structureStructure Gram +

or -Chemical Composition

Function

Ribosomes

Granules

Both

Both

70s

30s

50s

Glycogen, lipids, polyphosphate, etc.

CHON synthesis

Storage

Structure Gram + or -


Function

Endospores Gram + only Keratin coat, calcium dipicolinate

Resistance to heat, chemicals and dehydration

Internal Bacterial structure

Physiology, Growth and Nutrition Nutritional Requirements:1. Source of Carbon

A) Heterotrophs/ OrganotrophsB) Autotrophs/ Lithotrophs

photo-chemo-

2. Oxygen Requirement Obligate aerobes Obligate anaerobes Facultative anaerobes Microaerophiles Aerotolerant

3. Carbon dioxide

Capnophiles

PHYSICAL REQUIREMENTS

1. Redox potential (Eh)

Most culture media have Eh = +0.2 to +0.4V

Obligate anaerobes = requires – 0.2V

2. Temperature

Psychrophiles: -5 to 30 °C (opt 10-20) Mesophiles: 10 to 45 °C (opt 20-40) Thermophiles: 25 to 80 °C (opt 50-60)

3. pH

Acidophiles: 6.5 - 7.0 Neutrophiles: 7.5 - 7.8

**7.2 – 7.6 for medically important bacteria Alkalophiles: 8.4 – 9.0

BACTERIAL GROWTH

stationary

Log number log deathOf living cells/Tubidity

lag

Time (usually in hours)

Bacterial Cell and Its Ultra Structure Handouts

Documents

Transcript of Bacterial Cell and Its Ultra Structure Handouts