morphology of bacteria deepa babin

Morphology of bacteria

Deepa Babin

Travancore Medical college

Size of Bacteria

Average bacteria 0.2 – 1.5 micrometre (µm)in diam

.Resolution of unaided eye-200 microns

RBC is 7.5 µm in diam.

Cell

• The cell is the basic unit of life

• Based on the organization of the cellular

structures, cells can be divided into 2

groups:

• Eukaryotes-Fungi,Some algae,slime

moulds,Protozoa

• Prokaryotes-Bacteria,blue green algae

Morphology

Differences

Prokaryote Eukaryotes

Nucleus Absent (one circular) Present(linear more than one chromosome)

• Cytoplasm Absent Present

• Sterols Absent Present

• Muramic acid Present Absent

Shapes of Bacteria

• Coccus –Spherical or oval– Chain =- Streptoccus

– Cluster - Staphylococcus

– -Diplo-neisseria

• Bacillus– Chain - Streptobacillus

– Chinese letter pattern-Corynebacterium

• Coccobacillus -Acinetobacter

• Vibrio – curved or comma

• Spirillum –rigid spiral forms

• Spirochetes-flexible spiral forms

• Actinomycetes-branching spiral forms

• Mycoplasma-cell wall deficient

Coccus

Bacillus

Vibrio leptospira

Spirillum&Mycoplasma

Actinomycetes

Bacterial Cell

Bacterial Structures

• Cell Wall

• Plasma Membrane

• Cytoplasm

• Ribosomes

• Mesosomes

• Nucleus,plasmids

• Intracytoplasmic Inclusions

• Pili or Fimbriae

• Flagella

• Capsule/Slime layer

• L forms or Involution forms

• Spores

Cell Wall

• Determine shape of bacteria

• Strength prevents osmotic rupture

• 20-40% of dry weight of bacterial cell

• Does not stain with ordinary stains

• Some antibiotics effect directly– Penicillin

• Cell wall consists of Peptido-glycan Polymer (amino acids + sugars)

• Sugars-NAG (N acetyl glucosamine) & NAM-(N acetyl muramic acid)

• Arranged in alternating chains crosslinked by peptide chain

CELL WALL

• Gram positive cell wall contains thick layers of teichoic acid as surface Ag

• Gram negative thinner cell wall-contains

• 1. Lipopolysaccharide-lipid responsible for endotoxic activity,Polysaccharide for antigen specificity

• 2.Outer membrane –proteins known as porins-which permit the passage of small molecules

Cytoplasmic membrane(cell memb)

• Thin layer between cell wall enclosing

cytoplasm Bilayer Phospholipid

• Acts as a permeability barrier to & from

cytoplasm

• Respiratory enzymes are present

• Damage cause cell death

Cytoplasm

• 80% Water {20% Salts-Proteins)

– Osmotic Shock important

• Nucleus-devoid of nuclear memb so called

nucleoid

• DNA is circular, Haploid

• Attached to plasma membrane and replicates

by binary fission

• Ribosomes-protein synthesis-(Antibiotics like

T,Streptomycin acts on Ribosomes)

• Mesosomes-Invagination of plasma memb in

to cytoplasm- More Respiratory enzymes are

present

• Plasmids- extra circular DNA

– Mutation -Antibiotic Resistance

Intracytoplasmic Inclusions

• -They are reserve of energy mainly seen in

nutrient deficient condition

• -Mainly-Volutin,Lipids –

(Bacillus,TB),Polysaccharides-

(protozoa,fungus),crystals

• -Volutin - Babes-Ernst granules or

Metachromatic granules(reddish purple-

Albert’s or Neisser’s stain)

STRUCTURE OF FLAGELLA

Flagella

• Motility – movement

• Long hollow tubular structures attached to cell membrane(0.2µm)

• Viewed by Electron microscope

• Antigenic

• It consists of a Filament,Hook,Basal body

• Protein subunits called-“flagellin”

• Flagellum is attached to hook made up of different protein

• Basal body consists of outer and inner rings inserted in to small rod like structure,outer ring is attached to cell wall and inner ring attached to cell membrane.

• Basal body rotates flagellum either clockwise and anticlockwise to move bacteria

• Swarming occurs with some bacteria

– Spread across Petri Dish

– Proteus species most evident

• Arrangement basis for classification

– Monotrichous -Single flagella Eg:Vibrio cholerae

– Lophotrichous - Tuft at one end-Spirilla

– Amphitrichous - Single or tuft both ends-Pseudomonas

- Peritrichous- All around bacteria-Salmonella typhi

- Atrichous-No flagella

Arrangement

Lophotrichous -Lophotrichous -Lophotrichous -

Fimbriae

Fimbriae and Pili

• Short,thin hair like protein appendages made of protein subunits-Pillin

– smaller than flagella

– orginate from cell memb- Electron microscope

– organ of adhesion

– Fimbriae are antigenic

– E. coli has numerous types

• K88, K99, F41, etc.

• F1-Sex pili ; used in conjugation

– Exchange of genetic information

Capsule or Slime Layer

• Sticky,viscid bacterial secretion around cell surface

• Glycocalyx - Polysaccharide on external surface

• Adhere bacteria to surface– S. mutans and enamel of teeth

• Virulence factor

• -Prevents Phagocytosis

• Capsule can be demonstrated by negative staining with India ink preparation

• -Clear halo around bacteria against dark background

• Quellung reaction or Capsule swelling-( Neufeld)-Capsulated bacteria is mixed with its specific anticapsular serum and examined under microscope capsule becomes very prominent and appears swollen due to increase its refractivity

Capsule-negative staining

Endospores-

• Resistant structure-RESTING STAGE

– Heat, irradiation, cold

– Boiling >1 hr still viable

• Bacillus stearothermophilus -spores

– Used for quality control of heat sterilization

equipment

• Bacillus anthracis - spores

– Used in biological warfare

Endospore

Spore

• 1.Germinal groove

• 2. Outer cortical layer

3 . Cortex

• 4 .Internal spore coat

• 5 .Sub coat material

• 6. Outer spore coat

• 7 .Cytoplasmic membrane

• 8.Cell wall primordium

• Spores are destroyed by

AUTOCLAVING AT 121º C

FOR 15 MINUTES

1. Central bulging-

2.Central not bulging

3.Subterminal bulging

4. Subterminal not bulging

5.Terminal spherical

6. Terminal oval

Pleomorphism and Involution forms

-Due to defective cell wall synthesis -varies size

and shape

• L forms-Kleineberger-Nobel –Streptobacillus

moniliformis-swollen cells

• Due to Penicillin or other interference

Thank you