Bacterial morphology

G. Hariprasad M.Sc., M.Phil.,Lecturer in Microbiology

Department of MicrobiologyThoothukudi Govt. Medical College

Thoothukudi

ObjectivesThe student should be able to:Describe the typical bacterial cell based on

size, shape and groupings. Determine the medical importance of

certain structural components in a bacterial cell.

To discuss the appropriate staining procedure to demonstrate bacterial morphology and special structures.

To perform the following staining techniques Gram stainingAcid-Fast staining

ObjectivesDiscuss the growth requirements of bacteriaDifferentiate bacteria as to:

source of carbonsource of energytemperature requirementoxygen requirement

Discuss the bacterial growth curve lag phase logarithmic phasestationary phasedeath phase

SIZE OF BACTERIA

Unit for measurement : Micron or micrometer,μm: 1μm=10-3mm

Size: Varies with kinds of

bacteria, and also related to their age and external environment.

Cocci: sphere, 1μm Bacilli: rods , 0.5-1 μm in width -3 μm in length Spiral bacteria: 1~3 μm in length and 0.3-0.6 μm in width

MicroscopeBeam of light Beam of electron

Bacterial Morphology

Bacterial CellProkaryotes

No true nucleusNo organelles

Divide-binary fission

Parts of a CellCell envelope

Cell wall- murein sacculusOuter Cell membrane-plasma membrane, cytoplasmic

membraneCapsule

CytoplasmNucleiodRibosomesGranules/inclusion bodiesMesosomes

Parts of a Cell

SporesPlasmids

AppendagesPiliFlagella

Special components of Gram positive cell wall

Teichoic acid

SPA / M POTEIN

Special components of Gram

negative cell wall

Cell wall

PeptidoglycanN acetyl glucosamine & N acetyl Muramic acidProtect the cell from osmotic changesRigidityMultilayered in Gram positive

Teichoic acidMono to bi layered in Gram negative

Chapter 4

Chapter 4

Chapter 4

Chapter 4

Chapter 4

GRAM NEGATIVE CELL WALL

Chapter 4

Chapter 4

LPS UNIT

.Outer membrane- gram negative only

2 layers of lipidsInner layer-phospholipidsOuter layer- Lipopolysaccharide

3 regions Lipid A Core polysaccharide O antigen

Transmembrane proteinsPorins

Integral proteins

viability

Cytoplasmic MembraneLipid bi layer

Selective permeability

Site of ATP production

Viability

Chapter 4

Chapter 4

Chapter 4

Cell membrane

• Site of biosynthesis of DNA, cell wall polymers and membrane lipids. Selective permeability and transport of solutes into cells

• Electron transport and oxidative phosphorylation• Excretion of hydrolytic exoenzymes

CYTOPLASMNucleiod

Chromosomal DNAPlasmids

Inclusion bodiesStorage of excess food and energy

Metachromatic granules/ Babes ernst granules Much granule

SporesResist adverse conditionRibosome – 70s-50s & 30s

CapsulePolysaccharideAntiphagocyticantigenicVirulence

PiliCommon pili- fimbriaeSex pili- conjugationantigenic

Capsules and slime layers

These are structures surrounding the outside of the cell envelope. They usually consist of polysaccharide; however, in certain bacilli they are composed of a polypeptide (polyglutamic acid). They are not essential to cell viability and some strains within a species will produce a capsule, whilst others do not. Capsules are often lost during in vitro culture.

Attachment Protection from phagocytic

engulfment. Resistance to drying. Depot for waste products. Reservoir for certain

nutrients. protection

Pili

Pili are hair-like projections of the cell , They are known to be receptors for certain bacterial viruses. Chemical nature is pilin

Classification and Function

a.Common pili or fimbriae: fine , rigid numerous, related to bacterial adhesion

b.Sex pili: longer and coarser, only 1-4, related to bacterial conjugation

Flagella

Monotrichate/Amphitrichate/Lophotrichate/Peritrichate

Identification of Bacteria

Pathogenesis Motility of

bacteria

Some bacterial species are mobile and possess locomotory organelles - flagella. Flagella consist of a number of proteins including flagellinThe diameter of a flagellum is thin, 20 nm, and long with some having a length 10 times the diameter of cell. Due to their small diameter, flagella cannot be seen in the light microscope unless a special stain is applied. Bacteria can have one or more flagella arranged in clumps or spread all over the cell.

Flagella Locomotionantigenic

Plasmid Plasmids are small ， circular/line ， extrachromosomal， double-stranded DNA molecules 。 They are capable of self-replication and contain genes that confer some properties ， such as antibiotic resistance ， virulence factors 。 Plasmids are not essential for cellular survival. Inclusions of Inclusions of

BacteriaBacteria

Inclusions are aggregates of various compounds that are normally involved in storing energy reserves or building blocks for the cell. Inclusions accumilate when a cell is grown in the presence of excess nutrients and they are often observed under laboratory conditions.

granules

Nucleus

Lacking nuclear membrane, absence of nucleoli, hence known as nucleic material or nucleoid, one to several per bacterium.

Chapter 4

EndosporesResistant structure

Heat, irradiation, coldBoiling >1 hr still viable

Takes time and energy to make sporesLocation important in classification

Central, Subterminal, TerminalBacillus stearothermophilus -spores

Used for quality control of heat sterilization equipment

Bacillus anthracis - spores Used in biological warfare

• Dormant cell Dormant cell • Resistant to adverse Resistant to adverse

conditions conditions - high temperatures- high temperatures- organic solvents- organic solvents

• Produced when starvedProduced when starved• Contain calcium dipicolinateContain calcium dipicolinate DPA, DPA, DDipicolinic acidipicolinic acid• BacillusBacillus and and ClostridiumClostridium

Identification of Bacteria

Pathogenesis Resistance

SPOROGENESIS

Chapter 4

Spore stain

Chapter 4

Mesosomes• Mesosomes are specialized structures

formed by convoluted inveigh-nations of cytoplasmic membrane, and divided into septal and lateral mesosome.

MetabolismGlucose catabolism

EMP pathway

HMP

Etner duodoroff

TCA

ETC

Fermentation Homolactic fermentation

Heterolactic fermentation

Mixed acid fermentation

Peptidoglycan synthesis

PhysiologyNutritional requirement

Carbon Lithotropic Heterotrophic

NitrogenInorganic ionsGrowth factors

Physical RequirementsOxygen

Superoxide dismutase Catalase

Redox potentialTemperaturePhOsmotic condition

Spheroplast Forms in gram negative bacterium

Protoplast When lysozyme acts

on Gram positive bacterium in a hypertonic solution, a protoplast is formed.

L-FormsL-form bacteria, also known as L-phase

bacteria, L-phase variants, and cell wall-deficient (CWD) bacteria, are strains of bacteria that lack cell walls.[1] They were first isolated in 1935 by Emmy Klieneberger-Nobel, who named them "L-forms" after the Lister Institute in London where she was working[2].

Two types of L-forms are distinguished: unstable L-forms, spheroplasts that are capable of dividing, but can revert to the original morphology, and stable L-forms, L-forms that are unable to revert to the original bacteria.

L FORMS

Hydrogen ion concentration

Bacterial growth cycle

Lag

Stationary

deathlog

No of viable cell

time

Different Temps For Different BacteriaBacteria are grouped into three categories for optimum temperature-based growth: psychrophilic, mesophilic and thermophilic. Phileo in Greek means "lover of."Psychro- means low temperature. Psychrophilic bacteria are bacteria that grow best in low temperatures, such as 32 to 68 degrees F.

Examples of psychrophilic bacteria are basic soil bacteria like arthrobacter and psychrobacter. Arthrobacter is bacteria that helps neutralize the poisonous effects of some pesticides and nicotine, but psychrobacter is a cause of diseases like meningitis.

Meso- means "moderate or middle." Mesophilic bacteria grow best in lukewarm to cool warm temperatures, or 77 to 113 degrees F.

Different Temps For Different Bacteria – Contd.,

Thermophilic (thermo- means "hot or heat") bacteria grow best in warm to hot temperatures, or 122 to 158 degrees F.

Examples of thermophilic bacteria are Bacillus flavothermus and Thermus aquaticus. Bacillus flavothermus is a spore-forming bacteria found in soils. Thermus aquaticus lives in hot water. It is an important bacteria that helps humans, plants and animals code, recode and reproduce DNA and RNA with precision.

Hyper means "above." Hyperthermophilic bacteria will grow in very hot temperatures,- 122 degrees F–

Eg. Methanopyrus kandleri.

Different Temps For Different Bacteria – Contd.,

Methanopyrus kandleri.(HYPERTHERMOPHILES)

This slideshow presentation is dedicated to my beloved Microbiology students

Thank you!!!!!