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!!!!!