Plant Bacteriology (Pl. Path 503)

1. INTRODUCTION TO
PHYTOBACTERIOLOGY
Dr. K. T. Apet
Dr. D. S. Kadam
Department of Plant Pathology,
VNMKV, Parbhani

2. WHAT IS
PHYTOBACTERIOLOGY?
Phytopathology or plant bacteriology is
subdiscipline of Plant Pathology, which deals
with plant associated prokaryotes and their
interactions with each other and with their
hosts (Dumenyo et al., 2001)
Basic aspects:
 Morphology
 Physiology
 Taxonomy
 Genetics
 serology
Applied
 Host-pathogen
interactions
 pathogenesis
 infection process
 Epidemiology
 effect of
environment on

3. WHY STUDY THE
PHYTOBACTERIOLOGY
Past emphasis:
Investigation of plant diseases caused by bacteria due
to heavy losses caused by these diseases.
Current Scenario:
The field of Phyto bacteriology has expanded
considerably to include beneficial bacterial-plant
interactions such as nodulation and nitrogen fixation;
promotion of plant growth by phyllosphere,
rhizosphere and soil-inhabiting bacteria, and control
of ice-nucleation active bacteria by phyllosphere
bacteria.

4. What is Ice Nucleation
bacteria?
Ice nucleation active (INA) bacteria is a group
of bacteria with the ability to catalyse the ice formation
at temperature above -10°C and causing frost injury in
plants. Since, most of the literature on
INA bacteria were from subtropical area, studies of
INA bacteria from tropical area are needed.
Eg. The role of ice nucleation active Pseudomonas
viridiflava in frost injury to kiwifruit plants

5. How we can differentiate Prokaryotes with
Eukaryotes?

6. HOW TO CHARACTERISE
PROKARYOTES?
Prokaryotes lack an organized nucleus and other
membrane-bound organelles.
Prokaryotic DNA is found in a central part of the
cell called the nucleoid.
The cell wall of a prokaryote acts as an extra layer
of protection, helps maintain cell shape, and
prevents dehydration.
Prokaryotic cell size ranges from 0.1 to 5.0 μm in
diameter.
The small size of prokaryotes allows quick entry
and diffusion of ions and molecules to other parts of
the cell while also allowing fast removal of waste
products out of the cell.

7. GENERAL STRUCTURE OF
PROKARYOTE CELL

8. Prokaryotes comprises two groups
Bacteria
Archaea

9. HOW THEY DIFFERENTIATED?
Archaea Bacteria
Reproduction and Growth
Asexual Reproduction, by the process of
fragmentation, budding and binary fission
Asexual Reproduction. Eubacteria produces
spore to stay latent for several years.
Cell Membrane
Pseudopeptidoglycan Lipopolysaccharide/ Peptidoglycan
Metabolism Activity
Methanogenesis Autotrophy, Aerobic and Anaerobic
Respiration, Fermentation and
Photosynthesis.
RNA
Consists of three RNA Consists of single RNA
Thriving Habitat
Can sustain in extremely harsh
environment such as oceans, hot springs,
marshlands, hot springs and gut of humans
They are generally found in soil, organic
matter, earth’s crust, water, bodies of
animals and plants, radioactive wastes, hot
springs etc.

10. BACTERIA
Three subgroups on the basis of Gram reaction and Cell wall
a) Gram negative bacteria having cell walls
b) Gram positive bacteria having cell walls
c) Bacteria lacking cell walls

11. Gram negative bacteria having cell
walls
Outer membrane composed with thin peptidoglycan
layer containing muramic acid
Reproduction is usually by binary fission, some
show budding and a very few divide by multiple
fission.
occur in the form of spheres, ovals, straight or
curved rods, helical, or filamentous.
The cells may be nonmotile or motile showing
swimming or gliding motility.
members may be aerobic, anaerobic, facultatively
anaerobic, or microaerophlic.

12. Gram-positive bacteria having
cell walls:
No outer membrane and the peptidoglycan layer is
relatively thicker than that of Gram-negative type
of cell wall.
shapes include rods, spheres, or filaments; the rods
and filaments may show true branching.
The reproduction is mostly by binary fission but
actinomycetes and their relatives produce
sporogenous hyphae.
some members produce spores, also called
endospores (resting structure)
The oxygen requirement of the members is the
same as that of Gram-negative bacteria.

13. Differentiation on cell wall
basis

14. Bacteria lacking cell walls:
They are commonly called the "Mycoplasmas" (also
called mollicutes or soft-skin microorganisms).
They lack the cell wall but are enclosed, plasma
membrane.
 they lack the cell wall (peptidoglycan layer)
they are not sensitive to β-lactam antibiotics or other
antibiotics, which inhibit cell wall synthesis.
They are highly pleomorphic, and some forms are
filterable.
Cells stain Gram negative
no resting forms are produced, and usually
they are nonmotile but some members show gliding
motility. Different modes of reproduction budding,
binary fission, fragmentation

15. Most members require complex media and
require cholesterol or related sterols for
growth
The typical colony under adequate growth
conditions is biphasic having fried-egg
appearance
The mol% G + C contents of r RNA (43 - 48)
and of DNA (23 - 46) are lower than that of
walled bacteria.

17. ARCHAEA
Inhabitants of terrestrial and aquatic habitats, are found in
anaerobic, hypersaline, or hydrothermally and geothermally
heated environments.
Some members also live symbiotically in the digestive tracts of
animals.
Mesophiles and thermophiles
Grow as aerobes, anaerobes, and facultative anaerobes.
Cell walls do not contain murein, peptidoglycan containing
muramic acid, hence archaea insensitive to 𝛽-lactam
antibiotics
All archaea contain glycerol isopranyl ether lipids
Spherical, spiral, plate or rod.

18. The modes of reproduction include binary fission,
budding, fragmentation, constriction or mechanisms
not yet known.
The cell masses exhibit a variety of colours
including red, pink, purple, green, yellow, gray,
white, etc.
Five major groups recognized in archaea are given
below.
(A) Methanogenic archaea
(B) Sulphate-reducing archaea
(C) Extremely halophilic archaea
(D) Cell wall-lacking archaea
(E) Extremely thermophilic s°-metabolising

19. ECONOMIC IMPORTANCE OF
PHYTOPATHOGENIC PROCARYOTES
Pathogen Disease Loss (mUSD)
Ralstonia solanacearum Bacterial wilt of tomato
and
tobacco
9.4
Agrobacterium tumefaciens Crown gall of fruit and nut 23.0
Erwinia amylovora Fire blight of pear 4.7
Pectobacterium
atrosepticum
Black leg and/or soft rot of
potato
14.0
Pseudomonas savastanoi pv.
glycinea
Bacterial blight of soybean 65.0
Psm. syringae pv. syringae Bacterial leaf blight of
wheat
18.0
Leifsonia xyli subsp. xyli Ratoon stunting disease of
sugarcane
10.0

20. THANK YOU!