Bacterial morphology and classification.pptx

1. MICROBIOLOGY

2. BACTERIAL MORPHOLOGY AND
CLASSIFICATION
Submitted to,
Dr. Aghil soorya
Assistant Professor
ST. Teresa’s College, Ekm
Submitted by,
A. T Milin Sera
1st M. sc. Botany
ST. Teresa’s College, Ekm

3. Bacteria Morphology
 The word bacterium (Gk. Bakterion = little rod) originally applied
by microscopists for rod shaped organism, belonging to the
lowest order of the plant life or “microscopic unicellular plants
without chlorophyll that reproduce by fission”.
 Anton Van Leeuwenhoek (1632-1723), the Dutch dry goods
merchant of Holland, is credited with the discovery of bacteria.
 He observed bacteria in the scum of teeth with the help of
microscope constructed by himself. He named them as “tiny
animalcules”.
 In 1695 he published his work “The secrets of nature discovered
by Anton Van Leeuwenhoek” for this discovery he has been
called as “Father of Bacteriology”.

4.  Later Ehrenberg (1829) coined the term bacteria for these
microorganism. The term bacteria literally means, small stick.
 Carl Weigert (1845-1904) developed the staining technique for
bacteria. T.J. Bwoul (1878) said that the bacteria causes diseases
in plants.
 Bacteriology is the branch of botany under which we study the
metabolism and reproduction of bacteria.

5. General characters of bacteria:
 They are omnipresent i.e. present in soil, air and water.
 They are unicellular, prokaryotic microorganism.
 Because of the prokaryotic nature they lack true nucleus (lacking
nuclear membrane and nucleolus), genetic material is in the
form of composite structure known as genophore/ nucleoid/
incipient nucleus.
 The cell bears a thick rigid cell wall outside the plasma
membrane (because of this character they are kept in plant
kingdom).
 They lack true chlorophyll but few photosynthetic bacteria have
a special type of chlorophyll called bacteriochlorophyll.

6.  They have great variation in the mode of nutrition i.e. may be
autotrophic and heterotrophic. In heterotrophism mode of
nutrition they may be parasite, saprophyte or symbiotic in
nature.
 The cell wall of bacteria is made up of mucopeptide, lipoprotein
and lipopolysaccharide unlike the cell wall of plants (where it is
made up of cellulose).
 The surface appendages of bacteria include flagella, fimbriae
and pili.
 They lack mitochondria, golgi apparatus, plastid and endoplasmic
reticulum.
 They lack basic protein histone in their DNA.

7.  Ribosomes are of 70s type.
 At some places the plasma membrane invaginate in folds to form
mesosomes.
 All the enzymes required for respiration are found in the cell
membrane.
 Both DNA and RNA are present in the bacterial cell. DNA is in the
form of single circular chromosome (therefore the cell is
haploid).
 Vegetative reproduction is generally by binary fission, cyst,
budding and gonidia.
 Asexual reproduction is by conidia, motile spores and endospore.

8.  True sexual reproduction is absent in bacteria but there are
examples of genetic recombination which may be of following
types viz. conjugation, transduction and transformation.

9. Size Of Bacteria:
 There is great variation in size of bacteria. They are so minute
which can’t be seen without the help of microscope.
 On an average each cell of bacterium measures 1.25-2 μm in
diameter and 2-10 μm in length.
 Cocci are about 0.5-2.5 μm in diameter while bacilli are 0.3-15 μ
× 0.2 -21 μ.
 The smallest rod shaped eubacterium is Dialister pneumosintes
which measure in between 0.15μ- 0.31μ in size.
 The biggest bacteria Beggiatoa mirabilis is about 16-45 μ in
diameter and 80μ in length.

11. Morphological Forms Of Bacteria:
Bacterial cells differ in their shapes but usually three conventional
shapes have been recognized. Initially the classification of bacteria
was based on their shapes but now it is not used. The various
shapes are as follows:
1.Ellipsoidal/ Spherical/ Cocci
 The term cocci has originated from a Greek word; kokkos = grain
or kernel.
 It is the simplest form of bacteria in which bacteria appears like a
minute sphere (0.5~-1.25~ in diameter) they lack flagella.
 On the basis of arrangements cocci are further classified as
follows:

12. (i) Micrococci: When a bacterium appears singly e.g. Micrococcus
agitis, M. aureus.
(ii) Diplococcus: When they appear in a pairs of cells e.g.
Diplococcus pneumoniae.
(iii) Streptococci: When they appear in rows of cells or in chains e.g.
Streptococcus lactis.
(iv) Staphylococci: When they arrange in irregular clusters like
bunches of grapes e.g. Staphylococcus aureus.
(v) Tetracoccus: When they arrange in a sequence of four e.g.
Neisseria and Micrococcus tetrogenus.
(vi) Sarcinae: When they arrange in cuboidal or in a different
geometrical or packet arrangements e.g. Sarcillae lutea.

13. 2. Rod shaped bacteria or Bacillus
 The word bacillus originated from Greek word, bacillii means rod
or stick.
 Their ends are rounded flat or pointed.
 They may be flagellated or non-flagellated.
 Most of the bacteria causing disease in plants belongs to bacilli
category. They may be of following types:
(i) Monobacillus: When they arrange singly.
(ii) Diplobacillus: When they are present in a group of two e.g.
Diplobacillus pneumoniae.
(iii) Streptobacillus: When they appear in chains e.g. Bacillus
tuberculosis.
(iv) Palisade: Very rarely the bacillus arrange in a palisade
arrangement.

14. 3.Coccobacilli
Bacteria intermediate between Cocci and bacilli in shape are called
coccobacilli.
4.Spiral or Helical
The origin of word is from Greek word; spira means coiled. They
appear like a cork screw. A single spirillum has more than one turn
of helix. Generally they are found as free living, unicellular entity.
Their size ranges from 10-50~ in length and 0.5 – 3~ in diameter.
They are flagellated e.g. Spirillum minus, S. volutans.
5.Vibrio or Coma
The bacteria of this group are like ‘coma or small curved rod. They
bear flagella at their end. Their size ranges from 1.5-71μ in diameter
and upto 10μ in length e.g. Vibrio cholarae.

15. 6.Spirochaeta
 These bacteria appears like a cork screw and atrichous.
 Their length is more as compared to their diameter.
 Their body is more flexible.
7.Filamentous
 These type of bacteria are generally found in sewage water and
the water coming out from sugar industry or effluent of sugar
industry e.g. Sphaerotilus natalls.
 Basically they are rod shaped bacilli which grow in an elongated
chain and are covered by a tubular envelope.
 Ferrous containing water generally contain filamentous bacteria
e.g. Leptothrix, Cladothrix, Nocardia and Beggiatoa.

16. 8. Actinomycetes
Actinomycetes (actin, ray; mykes, fungus) are branching filamentous
bacteria resembling fungi. They possess a rigid cell wall.
9. Stalked
 These bacteria are enveloped by a extra cellular structure which
encloses the entire cell.
 This structure is known as prosthecae which is a slightly hard
appendage appendacular structure.
 Because of the presence of Prosthecae they are known as prosthecate
bacterium.
 These bacteria are classified in following two groups:
(a) The bacteria in which prosthecae does not take part in reproduction
e.g. Colobacter.
(b) The bacteria where prosthecae participate in reproduction e.g.
Hypomicrobium.

17. 10. Pleomorphic
 Many bacteria change their shape and structure with the change in
environmental conditions. These bacteria which are found in various
forms are known as pleomorphic bacteria e.g. Acetobacter.
11.Budding Bacteria
 These are of football shaped structure with a swollened part and a thin
tube. This tube gradually increases in size and its terminal end swells
up to form new cell which is globular and ultimately a net work of cell
is formed e.g. Rhodomicrobium.
12.Myxobacteria
 Bacteria without flagella and a rigid cell wall. They display gliding
movement. The individual cells are cigar-shaped, and they divide by
binary fission. The cells live as a colony in a common slimy mass.

20. Classification of Bacteria
 Bacterial systematics has undergone several changes and is
continuously in a state of flux as our knowledge of
microorganism is far from complete and new information is
being added every day.
 In 1923 David Bergey, professor of bacteriology at the University
of Pennsylvania and four colleagues published a classification of
bacteria that could be used for identification of bacterial species.
 The Bergey’s manual of determinative bacteriology has been a
widely used reference since publication of the first edition in
1923.

21.  The manual does not classify bacteria according to evolutionary
relatedness but provides identification (determining) schemes, based
on such criteria as cell wall composition, morphology, differential
staining, oxygen requirement and biochemical testing.
 From 1984, the Bergey’s Manual was renamed Bergey’s Manual of
systematic bacteriology is being published in separate volumes.
 This manual includes 35 sections based on characters like general
shape, morphology, gram staining, presence of endospore,
motility, oxygen relationships, mode of energy production.
 The manual include four divisions of the kingdom Prokaryotae.
The Gracilicutes (gram –ve cell wall) Firmicutes (gram + ve cell
wall other than actinomycetes), Tenericutes (bacteria lacking cell
wall other than actinomycetes) and Mendoricutes (bacteria
lacking peptidoglycan in their cell wall like Archaebacteria).

23. Bergey’s Manual of Systematic Bacteriology (1984- 2012) : Its 1st edition (4volumes) was
published in 1984-1989 and 2nd Edition (5 volumes) was published in 2001-2012.
Bergey’s Manual of Systematic Bacteriology:
 First edition -Published in 4 volumes:
 Volume 1 (1984) – Gram – negative Bacteria of general, medical, or industrial
importance.
 Volume 2 (1986) – Gram – positive Bacteria other than Actinomycetes.
 Volume 3 (1989) – Archaeobacteria, Cyanobacteria, and remaining Gram-negative
Bacteria.
 Volume 4 (1989) – Actinomycetes.
 Second Edition – published in 5 volumes
 Vol 1 – (2001) The Archaea and the deeply branching and phototrophic bacteria.
 Vol 2 – (2005) -The Proteobacteria.
 Vol 3 – (2009) – The Firmicutes.
 Vol 4 – (2011) – The Bacteroidetes, Spirochaetes, Tenericutes (Mollicutes),
Acidobacteria, Fibrobacteres, Fusobacteria, Dictyoglomi, Gemmatimonadetes,
Lentisphaerae, Verrucomicrobia, Chlamydiae, and Planctomycetes.
 Vol 5- (2012) – The Actinobacteria.

25. Volume I
Domain: Archaea
Phylum Crenarchaeota
Class: Thermoprotei
 Originally containing thermophilic and hyperthermophilic
sulfur-metabolizing archaea.
 Recently discovered Crenarchaeota are inhibited by sulfur
& grow at lower temperatures.
 Eg. Sulfolobus.

26. Domain: Archaea
Phylum Euryarchaeota
 Differ in rRNA from other archaeans
 Eight classes and twelve orders
 Methanogenic archaea – Methanococcus
 Halophilic archaea –Halobacterium
 Thermophilic – Thermococcus
 Sulfur-reducing archaea – Archaeoglobus

27. Domain Bacteria
 The 2nd edition of Bergey’s Manual of Systematic
Bacteriology divides domain Bacteria into 23 phyla. Some
notable phyla are:
Phylum Aquificae
 Contains genera Aquiflex and Hydrogenobacter that can
obtain energy from hydrogen via chemolithotrophic
pathways
 Also thermophilic

28. Phylum Thermotogae
 Anaerobic, thermophilic, fermentative, gram-negative
 Contains unusual fatty acids and ether linked lipids
 Also thermophilic
 E.g. Thermotoga
Phylum Deinococcus-Thermus
 Radiation resistant
 Stains Gram-positive
 High carotenoid contents

29. Phylum Chloroflexi
 Gram negative green nonsulfur bacteria
 Gliding motility
 Anoxygenic photosynthesis
 Unusual peptidoglycans and lack LPS
 Herpetosiphon (Nonphotosynthetic)
Phylum Cyanobacteria
 Oxygenic photosynthetic bacteria
 Chlorophyll a and phycobilins
 Unicellular or filamentous
 Some are Nitrogen fixers
 Nostoc, Spirulina

30. Phylum Chlorobi
 The “green sulfur bacteria”
 Anoxygenic photosynthesis
 Includes genus Chlorobium

32. VOLUME II
 Exclusive for Gram-negative bacteria
Phylum Proteobacteria
 The largest group of gram-negative bacteria
 Extremely complex group, with over 538 genera and 2000
species
 All major nutritional types are represented: phototrophy,
heterotrophy, and several types of chemolithotrophy
 Many species are important in medicine, industry and biological
research
 Five classes – (i) Alphaproteobacteria, (ii) Betaproteobacteria, (iii)
Gammaproteobacteria, (iv) Deltaproteobacteria, (v)
Epsilonproteobacteria

33. Class Alphaproteobacteria:
 Use Organically decomposed materials in anoxic zones
 Alcaligenes, Nitrosomonas, Methylobacillus
 Pathogen –Neisseria
Class Betaproteobacteria
 Largest class
 14 orders and 28 families
 Many facultative anaerobes
 Enterobacteriaceae, Vibrionaceae and Pasteurellaceae – Use EMP and
HMP pathways
 The family Enterobacteriaceae, the “gram-negative enteric bacteria,”
include genera Escherichia, Proteus, Enterobacter, Klebsiella,
Salmonella, Shigella, Serratia, and others

34. Class Gammaproteobacteria:
 Pseudomonadaceae, Azotobacteraceae use ED and HMP pathways
 The family Pseudomonadaceae, which includes genus Pseudomonas
and related genera
 Few are photosynthetic – Chromatium
 Methylotrophic – Methylococcus
Class Deltaproteobacteria:
 Eight orders and 20 families
 Predators - Bdellovibrio
 Myxococcales (Slime bacteria)
Fruiting myxobacteria – Myxococcus, Polyangium
Anaerobic sulfate reducers - Desulfovibrio

35. Class Epsilonproteobacteria:
 Only one order – Campylobacterales
 Campylobacter, Helicobacter
 Many are microaerophilic

36. VOLUME III
Phylum Firmicutes
 “Low G + C gram-positive” bacteria (less than 50%)
 Divided into 3 classes
Class I – Clostridia
 Includes genera Clostridium and Desulfotomaculum, and others
 Anaerobic
 Forms endospore

37. Class II – Mollicutes
 Called as mycoplasmas
 Lack cell wall
 Cell membrane –sterols are present
 Pleomorphic
 Require sterols for growth
 Normally non motile, but some exhibit gliding movement
 Most are Animal and plant pathogens
 E.g. Mycoplasma, Spiroplasma

38. Class III– Bacilli
 Gram positive
 Can be rods or cocci
 Mostly aerobic, some are facultative
 Two orders – Bacillales, Lactobacillales
 Medically and Industrially important genera
 Require sterols for growth
 E.g. Bacillus, Lactobacillus, Streptococcus, Staphylococcus,
Lactococcus, Enterococcus

40. VOLUME IV
Phylum Planctomycetes
 Aquatic habitats
 Coccoid, ovoid or pear shaped
 Some have membrane-enclosed nucleoid
 Most of them lack peptidoglycan
 Unicellular as well as chains
 Division by budding
 Flagellar or giding motility
 E.g. Isophaera

41. Phylum Chlamydiae
 Obligate intracellular parasites
 Coccoid
 Very small in size
 Two stages in life cycle – elementary bodies and reticulate bodies
 Most of them lack peptidoglycan
Phylum Spirochaetes
 Characterized by flexible, helical cells with a modified outer membrane (the
outer sheath) and modified flagella (axial filaments) located within the outer
sheath
 Gram negative
 Chemoheterotrophs
 Free living, symbiotic or parasitic
 Important pathogenic genera include Treponema, Borrelia, and Leptospira

42. Phylum Bacteroidetes
 Gram negative, non spore forming anaerobic, rods
 Wide distribution – soil, sea, guts and skin of animals
 Fecal Indicator
 Beneficial microbe in the gut
 Some are opportunistic pathogens
 Resistant to wide range of antibiotics
 Includes genera Bacteroides, Flavobacterium, Flexibacter, and
Cytophaga are motile by means of “gliding motility”

43. VOLUME V
Phylum Actinobacteria
 “High G + C gram-positive” bacteria
 Terrestrial or aquatic
 Only one class, but 5 subclasses, six orders and 44 families
 Often form complex branching filaments called hyphae
 Even complex life cycles are found in some genera
 Forms asexual spores

44. Phylum Actinobacteria
 Secondary metabolite producers
 Varied difference in their cell walls, e.g. mycolic acid
 Largest genus Streptomyces – 150 species
 Includes genera Actinomyces, Streptomyces, Corynebacterium,
Micrococcus, Mycobacterium, Propionibacterium

46. Thank you