Brief introduction History Characteristics Morphology Classification Nutrition Structure Reproduction Economic importance of bacteria

1. BACTERIA
Prepared by
Khansa Amber
Lecturer Dept. of Botany
Govt.College Mansehra

2. Contents
 Brief introduction
 History
 Characteristics
 Morphology
 Classification
 Nutrition
 Structure
 Reproduction
 Economic importance of bacteria

3. INTRODUCTION TO BACTERIA
 Bacteria are microscopic organisms.
 ‘germs’ and ‘microbes’.
 Smallest and simplest cellular organism.
 Bacteria + Cyanobacteria (Blue-Green algae)
placed in separate kingdom Monera.
 Prokaryotic.

4. History of bacteria
 1976 – Leawon hook (Father of microbiology) ----
-Microorganisms
 Louis Pasture---confirmed---presence.
 Robert kotch----discovered---1st bacteria

5. CHARACTERISTICS OF BACTERIA
 Unicellular
 Colonial
 Diameter between 1-5 μm
 Prokaryotic
 Cosmopolitan
 While several bacterial species are
pathogenic (capable of causing disease)
 Most are non-infectious.

6.  Many have critical roles in
 Decay
 Fermentation
 Nutrient recycling
 Nitrogen fixation.
 Bacteria are usually classified as gram
positive or gram-negative based on a basic
microbiological staining procedure called the
gram stain.
 They come in a variety of shapes and sizes.

7. MORPHOLOGY
 Bacteria display a wide diversity of shapes and sizes called
 morphologies
 Cannot be seen with human eyes (microscopic)
 Their presence was only first recognized in 1677, when the Dutch
 naturalist Antonie van Leeuwenhoek saw microscopic organisms
 in a variety of substances with the aid of primitive microscopes.
 Now bacteria are usually examined under light microscopes
 capable of more than 1,000-fold magnification
 Details of their internal structure can be observed only with the
 aid of much more powerful transmission electron microscopes.
 Unless special phase-contrast microscopes are used, bacteria
 have to be stained with a coloured dye so that they will stand
 out from their background.

8. CLASSIFICATION OF BACTERIA
 With over millions of bacteria
present in the planet, it
 is not an easy job to identify,
isolate and study a
 particular species or particular
bacteria as such.
 • Microbiologists categorized
bacteria based on basic
 and important factors making all
the bacteria fall under
 any one of the categories and
thus making the process
 of isolation and identification
much easier.
 • Bacteria are classified based
on various factors like
 shape (morphology), Cell wall
structure, Respiration
 (metabolism), type of nutritional
source, characteristic
 and environmental factor.
 Bacteria are classifiedbased on
 various factors
 • shape (morphology)
 • Cell wall structure
 • Respiration (metabolism)
 • type of nutritional source
 • characteristic
 • environmental factor etc.

9. Classification on the basis of
Stainning method Capsule
 Gram positive bacteria -
take up crystal violet dye
 andretain their blue or
violet color.
 Gram negative bacteria -
do not take up crystal
 violet dye, and thus appear
red or pink.
 •Capsulated
 • Encapsulated

10. Classification Based on
Spore Formation
Classification Based on
their association
 Spore forming
 Non-sporeforming
 With host
 Beneficial
 Pathogenic
 Harmless

11. Respiration
 AerobicRespiration :
Sugars are broken downin the
presence of oxygen to produce
carbondioxide, water, and
energy.
 Anaerobic Respiration :
breaks downsugars and releases
energy in theabsence of
oxygen.
Slower and less efficient than
aerobicrespiration.
Itinvolves chemicalsotherthan
oxygen and carbondioxide.
 FacultativeAnaerobic
Respiration:
Ableto perform either aerobic /
anaerobicrespiration
depending on theoxygen
contentof their environment.
E.g : Coliformbacteria
 Microaerophiles:
Sugars are broken downin the
presence of minute amountsof
oxygen to produceenergy.

12. Classification Based on
Environment
 Mesophiles- which require moderate temp to survive.
 Neutrophiles- require moderate conditions to survive.
 Extremophiles- can survive in extreme conditions.
 Acidophiles- which can tolerate low pH conditions.
 Alkaliphiles- which can tolerate high pH conditions.
 Thermophiles- which can resist high temperature.
 Psychrophiles- can survive extremely cold conditions.
 Halophiles- can survive in highlysaline conditions.
 Osmophiles- can survive in high sugar osmotic
 conditions.

13. Shape Flagella Colonization
 Cocci
 Bacilli
 Spirals
 Spirillum
 Spirochete
 Atrichous
 Monotrichous
 Amphitrichous
 Lopotrichous
 Peritrichous
 Cocci
 Monococcuss
 Diplococcuss
 Streptococcus
 Staphylococcus
 Tetracoccus
 Sarcinae
 Bacilli
 Monobacillus
 Diplobacillus
 Triplobacillus
 Spirals
 vibrios
 Spirilla
 Spirocheates

14. On the basis of shape
 Coccus: Spherical (round)
 Bacillus: Rod shaped
 Vibrio:Comma shaped with
flagella
 Spirillum: Spiral shape
 Spirochete: wormlike spiral
shape

15. On the basis of Flagella
 Atrichous
Withoutflagella
 Monotrichous
a single flagellumatone pole.
Amphitrichous
2 or more than 2 flagella onbothends
 Lopotrichous
Tuffofflagella on one side
 Peritrichous
Flagella throughoutthe surface

16. On the basis of colonization
 Cocci
 Monococcuss (One)
 Diplococcuss
 Streptococcus
 Staphylococcus
 Tetracoccus
 Sarcinae
 Bacilli
 Monobacillus
 Diplobacillus
 Triplobacillus
 Spirals
 vibrios
 Spirilla
 Spirocheates

17. Nutritional Source
1. Autotrophs:
Use inorganic source and synthesize
organic compounds. E.g
Obtainthe carbon it requires from carbon
dioxide
 Photoautotrophs:
Directlyuse sunlight in order to produce
sugarfrom carbondioxide
 Chemoautotrophs :
depend on various chemicalreactions.
 Use inorganicenergysources, such as
hydrogensulfide,elementalsulfur, ferrous
iron,molecularhydrogen, and ammonia.
2. Heterotrophs :
Rely on organic sources e.g lipids,
Carbohydrates etc.
3 types
 Saprotrophic Bacteria
Dead organicmatter
Decomposeandget food.
 Parasitic bacteria
Host May be
Facultative parasites
(not dependent completelyon host)
 Obligate parasites.
(host dependent)

18. STRUCTURE OF BACTERIAL CELL
 Capsule / Glycocalyx
 Pilli/ Fimbriae
 Flagella
 Cell wall
 Cell/ Plasma membrane
 Cytoplasm
 Chromosomes
 Ribosomes

19. Capsule / Glycocalyx
 Outside cellwall
 sugarcoatirregularseceretion ofpolysaccharides,
 capsule: tightly bound regulardistribution
 Protects and prevents from drying,also protects from phagocytes
*Slim layer:thin secretion ofpolysaccharides,and often a significant
componentof“biofilms”
2.Polysaccharidesfirmly attached to the cell wall.
 Capsules adhere to solid surfaces and to nutrients in the environment.
 Adhesive powerofcapsules is a major factor
in the initiation of some bacterialdiseases.
 Capsulealso protectbacteria from being
phagocitized bycells of the hosts immune system.
 Sticky layer
 Used to Adhere with
 With Substrate
 To form colonies
 ResistAntibiotics
 Shield pathogenic bacteriafrom attack
by Host’s Immune system

20. Pilli / Fimbriae
 Hollow filamentous rods
 Motile& non motile.
 Shortprotein appendages
 Smaller than flagella
 Fimbriae
 Bristlelike small/short fibres andnumerous.
 Present on bothGram positiveandGram negativebacteria.
 Cell to cell attachments
 Adhere bacteria to surfaces(hostepithelium)
 Fimbriaecan also detect chemical signals.
 Fimbriaealso act as receptors for bacteriophages.
 Pilli
 long hair like tubularmicrofibres like structures.
 Even thoughpiliarise from plasmamembrane they are not
consideredpart of theplasmamembrane.
 present only on someGram negative bacteria.
 F pillus /Sex pillus –bacterial mating—sexualreproduction.
 Used in conjugationfor Exchange ofgeneticinformation
 Aid Flotation by increasingbuoyancy

21. Flagella
 Motile
 Hair like, helical cytoplasmic appendages.
 ProkaryoticFlagella are much thinner than eukaryotic Flagella and they lack the
typical 9+2arrangement of microtubules.
 Theyare approximately 3-2μm long and end in a square tip.
 Thebacterial flagella is non-contractile, compose of single type of proteins subunits
called flagellin.
 With the help of Flagella bacteria can move at average speed of 50 μm/sec.
 Capable of “Taxis”
 Positive chemotaxis
 Movetowards nutrients
 Negative chemotaxis
 Moveaway from toxic substances
 Somebacteria are motile and some are not. Almost all motile bacteria possess
flagella as the organ of locomotion. Such bacteria tend to move towards or away
 fromthe source of stimulus .these stimuli can be chemicals, light, air or magnetism.

22. CELL WALL
 Cell wall – Murein (Peptidoglycan)
 5 amino acids
 N-acetyl glucosamine
 N-acetyl Muramic acid
 Rigidstructuregive shape to the
cell.
 Necessary for the growth and
development
 Maintains cell shape.
 Protect cell from osmotyic lysis
 Act as a barrier
 Attachment site for flagella
 Site of action of certain
antimicrobial agents

24. Types of bacteria on the basis of cell
wall

25. Plasma membrane
 Thin n elastic , can be only seen with electron microscope
 Phospholipids (20-30%) and protein (60-70%).
 5-10 nm in thickness.
 It lies below the peptidoglycan layer of the cell wall and encloses the cytoplasm.
 The arrangement of a lipid and protein to form a layer is called a
 It is a phospholipid bilayer with polar heads on rather side of the membrane .
 Phospholipid molecules oriented so that hydrophilic,water-loving heads directed
outward and hydrophobic ,water-hating tails directed inward.
 Proteins embedded in two layers of lipids (lipid bilayayer) (fluid mosaic model).
 Specialized structures called as mesomers or chondroids are present.

26. Functionof plasma membrane
 Housing enzymes for cell wall, outer membrane synthesis, assembly n secretion
of extractoplasmic n extracellular substances
 Semipermeable membrane
 Generation of ATP
 Cell motility
 Mediation of chromosomal segragation during replication
 Site of energy Production
 Attachment with bacterial DNA
 A selectively permeable barrier
 Integral proteins form channels
 Peripheral proteins can act as a receptors
 Excretion of hydrolytic enzymes
 Site for the initiation of cell wall synthesis
 Site of the attachment of the chromosome
 Site of synthesis of phospholipids
 Bear receptors and proteins of sensory transduction

27. CYTOPLASM
 The cytoplasm or protoplasm is the portion of the cell
that lies within the cytoplasmic membrane .
 It is a gel like structure and includes the prokaryotic
chromosomes and ribosomes.
 Constituents of cytoplasm include proteins, vitamins,
ions, nucleic acids and their precursors, amino acids
and their precursors, carbohydrates and their
derivatives, fatty acids and their derivatives.
 The cytoplasm does not exhibit any internal mobility.
 Cytoplasm also lacks organelles such as mitochondria,
Golgi apparatus and endoplasmic reticulum.
 Recent studies suggest that some bacteria possess
cytoskeleton.

28. RIBOSOMES
 Bacterial cells can contain thousands of ribosomes,
which are the sites of protein synthesis.
 The distinct granular appearance of prokaryotic
cytoplasm is due to the presence and distribution of
ribosomes.
 They often aggregate to form structures known as
polysomes.
 Bacterial ribosomes are termed 70s and eukaryotic
ribosomes are termed as 80s.
 The difference between the bacterial and eukaryotic
ribosomes is often exploited during antibiotic
therapy.

29. SPORE
 In poor growth conditions some bacteria produce resistant survival
forms termed endospores. This process is known as sporulation.
 They are resistant to extreme environmental conditions such as
higher temperature, dryness, toxic chemicals and UV radiations.
 Once the endospores are formed the vegetative portion of the
bacterium is degraded and the dormant endospore is released.
 The endospore is able to survive for long periods of time until the
environmental conditions again become favorable for growth.
Endospore forming bacteria
Clostridiumbotulinum, Bacillusbrevis, Bacillus thuringiensis

30. PROTOPLAST AND SPHEROPLAST
 When bacteria are treated with enzymes that
hydrolyze the cell wall are antibiotics that
interfere with biosynthesis of peptidoglycan,
wall-less bacteria are often produced.
 Such a treatment of bacteria in osmotically
protective medium liberates protoplast from
gram positive bacteria and Spheroplast from
gram negative bacteria.
 Spheroplast retains the outer membrane.
 They are produced more readily with penicillin
than with lysozyme.

31. Specialized membrane
Have infoldings to form complex
internal structure i.e mesosomes
and photosynthetic membranes.
Mesosomes
 Infolding.
 Associated to dna during cell
division.
 It help in seperation of two
daughter cells
 Provide surface area to cell
membrane for cellular respiration.

32. Photosynthetic membrane
 In photosynthetic bacteria.
 Tubular sheet like infoldings.
 Resembles thylakoid in cyanobacteria.
 Have photosynthetic pigment called Bacteriochlorophyll (Site of
photosynthesis)

33. Cytoplasm
a) Cytosol
b) Ribosomes
c) Chromosomes
a) Cytosol
Complex of inorganic acid, a.a, proteins,
peptides, nitrogenous bases, vitamin,
enzymes, co enzymes which provide chemical
environment for metabolic activities, cellular
activities.

34. b) Ribosomes
 RNA bodies
 Freely in cytoplasm
 Protein synthesis.
 2 subunits( 50 S + 30S)
 Consists of RNA and protein
 Abundant in cytoplasm
 Often grouped in long chains called polyribosomes.
 Smaller than the ribosomes in eukaryotic cells but have a similar function.

35.  They translate the genetic code from the molecular language
of nucleic acid to that of amino acids—the building blocks of
proteins.
 Bacterial ribosomes are similar to those of eukaryotes, but
are smaller and have a slightly different composition and
molecular structure.
 Bacterial ribosomes are never bound to other organelles as
they sometimes are bound to the endoplasmic reticulum in
eukaryotes, but are free-standing structures distributed
throughout the cytoplasm.
 There are sufficient differences between bacterial ribosomes
and eukaryotic ribosomes that some antibiotics will inhibit the
functioning of bacterial ribosomes, but not a eukaryote's, thus
killing bacteria but not the eukaryotic organisms they are
infecting.
 Streptomycin binds 70S ribosome and stops protein
synthesis but it can not bind 80S

36. c) Chromosome
 The chromosome in bacteria is typically a single,closed circle DNA that is concentratedin a nucleoid
region.
 Mitotic apparatus and nuclearmembraneare completelylacking.
 As in all organisms,bacterialDNA containsthe four nitrogenous bases A,G,C,T.
 The amount of DNA in bacterial chromosomes ranges from 580,000 base pairs in Mycoplasma
gallinarum to 4,700,000base pairs in E. coli to 9,140,000 basepairs in Myxococcus xanthus.
 Unlike the DNA in eukaryotic cells, which resides in the nucleus, DNA in bacterial cells is not
sequestered in a membrane-bound organelle but appears as a long coil distributed through the
cytoplasm.
 In many bacteria the DNA is present as a single, circular chromosome and in some cases the DNA is
linearratherthan circular.some bacteria may contain two chromosomes
 The bacterialchromosomeconsists ofa single,circle of deoxyribonucleic acid.
 DNA is double stranded- two strands line up antiparrallel to each other and the bases are linked
togetherwith hydrogenbondswhich includesmostof the genetic materialof the organism .

37. Plasmids
 Extra chromosomal circular DNA.
 • contain genes for antibiotic resistance or virulence.
 • Structure Similar to most bacterial chromosomes, but
considerably smaller..
 Size : Chromosomal DNA is typically about 4000 kb,
 plasmid DNA ranges from 1-200 kb.
 Number of plasmids: 1-700 copies of plasmid in a
 cell.
 Plasmids and the associated traits can be transferred
 between bacteria, even from one bacterial species to
 another.
 Plasmids are not involved in reproduction.
 Plasmids replicate independently of the chromosome.
 Plasmids are passed to other bacteria by two means.
 For most plasmid types, copies in the cytoplasm are
 passed on to daughter cells during binary fission.
 Consisted of few genes.
 Self replictiong.
 Certain plasmids
provideresistance to
antibiotics and disinfectants .
• Extra-chromosomal
circular DNA
• multiple copy number
• coding
 - pathogenesis
factors
 - antibiotic
resistance factors
• bacterial replication

38.  PlasmidFunction
 Thefunctionof plasmidsis not always known, but they
 are not normally essential for survival of host,although
 theirpresence generally gives thehostsome
 advantage.
 Antibioticresistance- Some plasmids code for proteins
 thatdegrade antibiotics-abig advantage forpathogens.
 Someencodefor proteins which confer virulence
 factorsonthehost.Forexample- E. coli plasmid Ent
 P307codes foran enterotoxin whichmakes E. coli
 pathogenic.
 Conjugativeplasmids –
Theseallow exchangeof DNA between bacterial cells.

39. Spores and cysts
 Bacteria produces
endospores e.g bacillus
spp.
 They can resist heat,
desiccation and
radiation to overcome
unfavorable conditions
Gas vacuole
 Hollow, rigid cylinders.
 Impermeable to water.
 In some aquatic
species hey provide
buoyancy.

40. Inclusion Composition
Glycogen poly-glucose Reservecarbonand energy
source
Poly-betahydroxybutyric acid
(PHB)
lipid Reservecarbonand energy
source
Poly-phosphates polymers ofPO4 Reservephosphate,possibly
high-energyPO4
Sulfurglobules elementalS Reserveenergyand orelectrons
Magnetosomes magnetite (iron oxide) Provide orientationin magnetic
field
Gas vesicles protein shells inflated with gases Provide buoyancyin aquatic
environments
Parasporalcrystals protein Produced by endospore-forming
Bacilli- toxic to insects

41. Reproduction in bacteria
• Cell growth and reproduction by cell division are
 tightly linked in unicellular organisms.
 Bacteria grow to a fixed size and then reproduce
 through binary fission, a form of asexual reproduction
 Under optimal conditions, bacteria can grow and
 divide extremely rapidly, and bacterial populations can
 double as quickly as every 9.8 minutes.
 In cell division, two identical clone daughter cells are
 produced.
 Budding involves a cell forming a protrusion that
 breaks away and produces a daughter cell

42. Binary fission
 Most prokaryotes reproduce by a process of binary fission, in
 which the cell grows in volume until it divides in half to yield two
 identical daughter cells.
 Each daughter cell can continue to grow at the same rate as its
 parent.
 For this process to occur, the cell must grow over its entire
 surface until the time of cell division, when a new hemispherical
 pole forms at the division septum in the middle of the cell.
 The septum grows inward from the plasma membrane along the
 midpoint and forms as the side wall which pinches inward,
 dividing the cell in two.
 In order for the cell to divide in half, the peptidoglycan structure
 must be different in the hemispherical cap than in the straight
 portion of the cell wall, and different wall-cross-linking enzymes
 must be active at the septum than elsewhere.

43. Budding
 A group of environmental bacteria reproduces by budding.
 In this process a small bud forms at one end of the mother
 cell
 As growth proceeds, the size of the mother cell remains
 about constant, but the bud enlarges.
 When the bud is about the same size as the mother cell, it
 separates. This type of reproduction is analogous to that in
 budding fungi, such as brewer’s yeast (Saccharomyces
 cerevisiae).
 One difference between fission and budding is that, in the
 latter, the mother cell often has different properties from the
 offspring. E.g : In some strains, mother cells have a flagellum and are
 motile, whereas the daughter buds lack flagella.

44. BACTERIAL RECOMBINATION
 Three mechanisms of genetic
recombination
 •Conjugation
 •Transformation
 •Transduction

45. CONJUGATION
Two bacterial cells come together and mate such that a gene transfer
occurs
 between them.
 Can only occur between cells of opposite mating types.
 – The donor (or "male") carries a fertility factor (F+).
 – The recipient ("female") does not (F−).
 One cell, the donor cell (F+), gives up DNA; and another cell, the recipient
 cell (F−), receives the DNA.
 The transfer is nonreciprocal, and a special pilus called the sex pilus joins
 the donor and recipient during the transfer.
 The channel for transfer is usually a special conjugation tubeformed
during
 contact between the two cells.
 The DNA most often transferred is a copy of the F factor plasmid.
 The factor moves to the recipient, and when it enters the recipient, it is
copied to produce a double-stranded DNA for integration.

46. BACTERIAL TRANSFORMATION
 • Discovered by Frederick Griffith in 1928.
 • Many bacteria can acquire new genes by taking up DNA
 molecules (ex: plasmid) from their surroundings.
 • When bacteria undergo lysis, they release considerable
 amounts of DNA into the environment.
 • This DNA may be picked up by a competent cell- one
 capable of taking up the DNA and undergoing a
 transformation.
 • To be competent, bacteria must be in the logarithmic
 stage of growth, and a competence factor needed for the
 transformation must be present.

47. BACTERIAL TRANSDUCTION
 Bacterial viruses ( bacteriophages)
transfer
 DNA fragments from one bacterium (the
 donor) to another bacterium (the
recipient).
 The viruses involved contain a strand of
DNA
 enclosed in an outer coat of protein.

48.  After a bacteriophage enters a bacterium, it may encourage the
 bacterium to make copies of the phage.
 At the conclusion of the process, the host bacterium undergoes
 lysis and releases new phages. This cycle is called the lytic cycle.
 Under other circumstances, the virus may attach to the bacterial
 chromosome and integrate its DNA into the bacterial DNA. It may
 remain here for a period of time before detaching and continuing
its
 replicative process. This cycle is known as the lysogenic cycle.
 Under these conditions, the virus does not destroy the host
 bacterium, but remains in a lysogenic condition with it. The virus is
 called a temperate phage, also known as a prophage.
 At a later time, the virus can detach, and the lytic cycle will
 ensue.
 It will express not only its genes, but also the genes acquired
 from the donor bacterium.

49. THANKYOU !