Morphology and structure of Morphology and structure of bacteriabacteria

Oral Microbiology for dentistry

MUDr. Lenka MUDr. Lenka ČČernohorskernohorská, Ph.D.á, Ph.D.

Size of bacteriaSize of bacteria

Pathogenic bacteria: mainly around Pathogenic bacteria: mainly around 1 – 5 1 – 5 μmμm (1 μm = 10 (1 μm = 10-3-3 mm) mm)

Staphylococcus: the diameter circa Staphylococcus: the diameter circa 1 μm1 μm Even Even smallersmaller: :

rickettsiae (circa 0.5 μm) rickettsiae (circa 0.5 μm) chlamydiae (elementary bodies circa 0.3 μm) chlamydiae (elementary bodies circa 0.3 μm) mycoplasmas (circa 0.2 – 0.25 μm ) mycoplasmas (circa 0.2 – 0.25 μm )

Various shapes of bacteriaVarious shapes of bacteria

• Cocci (spherical)Cocci (spherical)• Rods /bacilli:Rods /bacilli:

can be shortcan be short

longlong

robust, thinrobust, thin

• Spirochaete (helical)Spirochaete (helical)

Common bacterial formsCommon bacterial forms

• Cocci in chains – streptococci

• Cocci in clusters – staphylococci

• Cocci in pairs – diplococci (neisseria)

• Bacilli in chains

• Curved bacilli

• Spore-bearing bacilli

Bacterial cellBacterial cell

Structures I. – detail infoStructures I. – detail info

Structures II.Structures II.

CytoplasmCytoplasm - is enclosed within the cell membrane, contains organelles. Here occur most cellular activities and metabolic pathways. The part of the cytoplasm that is not held within organelles is called the cytosol (a gel, with a network of fibers dispersed through water)

CapsuleCapsule – gelatinous layer around the bacterium is composed of polysaccharides, proteins – inhibits phagocytosis, helps the adhesion, is used in preparation of vaccines

FimbriaeFimbriae – hair-like filaments, mediate adhesion to receptors

InclusionsInclusions – serve as sources of stored energy (polysaccharides)

Gram-staining Gram-staining (more in practical lessons)(more in practical lessons)

• Crystal violetCrystal violet – 30 s

• Iodine solutionIodine solution – 30 s

• AlcoholAlcohol – decolorize until violet is removed

• SafraninSafranin – 60 s

G+ purple groupsG- pink groups

Cell wallCell wallResults:• different in G- and G+ bacteria• principle of Gram staining is still unknown, but

it is used for hundred years • G+: Crystal violet attaches to peptidoglycan

(PG) than arise complex with IodineIodine, complex is not washed by alcohol, that is why the final result is purplepurple.

• G-: Little amount of PG inside a cell wall, a little complex/no complex? is washed by alcohol, Safranin is needed for visualisation.

Examples ofExamples of G+G+ andand G–G– microbesmicrobes

Gram-positives Gram-positives

StaStaphylococcusphylococcus

StreptococcusStreptococcus

BacillusBacillus

ClostridiumClostridium

ListeriaListeria

CorynebacteriumCorynebacterium

Yeasts Yeasts

Gram-negativesGram-negatives

EscherichiaEscherichia

SalmonellaSalmonella

Haemophilus Haemophilus

PseudomonasPseudomonas

MycoplasmaMycoplasma

FlagellaFlagella • filaments composed of flagellin flagellin

• responsible for movement movement of bacteria

May be located: (cocci and bacilli)

• at one end:monotrichous, a single flagellum

lophotrichous – many flagella

• all over the outer surface – peritrichous

• Spirochaets move by using the axial filamentaxial filament – produce undulation motion

Sporulation (bacterial winter sleep)Sporulation (bacterial winter sleep)

• In bad conditions some kind of bacteria sporulate

• Spora contains a high concentration of calcium dipicolinate, is resistant to heat, radiation, chemicals, dehydratation, it can remain for many years

• Better conditions- spore transform itself into reproducing bacterial cell again.

Sporulation processSporulation processseptum

Spores - factsSpores - facts

• Spore contains: DNA, small amount of cytoplasm, cell membrane, peptidoglykan, very little water, thick keratin-like coat (with calcium dipicolinate)

Relevance of bacterial sporesRelevance of bacterial spores

• Resistance to heat and chemicals!

• They cannot be easily achieved by boiling

• Other methods of sterilisation like autoclaving should be used

• So for ex. Bacillus stearothermophilusBacillus stearothermophilus is used for evaluation of the sterilisation efficacy of autoclaves!

Types of sporesTypes of spores

1, 4 – central

2, 3, 5 – terminal

6 - lateral

2 – with inclusions

3, 4, 5, 6 – spores deforming a bacterial cell

1, 2 – spores not deforming

SporesSpores

terminal

subterminal

central

Thank you for your attentionThank you for your attention

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