microbiology cell and its types

1. MARPHOGENISIS AND CELLULAR
DIFFERENTATION
V H VINUTHANA
PG20AGR12036
DEPARTMENT OF AGRICULTURAL MIROBIOLOGY

2. MARPHOGENISIS
The biological process that cause an organism to develop its shape
Greek word morphê means shape Genesis means creation
The word marphogenisis literally, means "beginning of the shape”
• It is one of three fundamental aspects of developmental biology along
with the control of:
• cell growth and
• cellular differentiation
• The process controls the organized spatial distribution of cells during the
embryonic development of an organism.

3. • Morphogenesis can take place also in a mature organism, e.g.
in inside tumor cell masses
• In unicellular animals, Morphogenesis also describes the
development of unicellular life forms that do not have an
embryonic stage in their life cycle.

4. BACTERIAL CELL WALL
MORPHOGENESIS
Bacteria have a peptidoglycan cell wall which maintains cell
shape and combats osmotic stress. Far from being static, the
peptidoglycan is highly dynamic and bonds are continually
broken and reformed to allow growth of the cell. Enzymes
that cleave specific bonds in peptidoglycan are ubiquitous
among bacteria and these enzymes are known as hydrolases.

5. NATURE OF BACTERIAL SHAPE
cells The most prevalent form of bacterial cell wall is the peptidoglycan (PG), a
structure composed of glycan strands made of repeating disaccharide subunits
composed of N-Acetylmuramic acid (MurNAc) and N-Acetylglucosamine
(GlcNAc), which are further crosslinked by pentapeptide bridges attached to the
MurNAc units
The morphogenesis of different bacterial shapes requires the spatiotemporal modulation
of the PG synthesis machinery
There are two major PG synthesis modes whose combination likely leads to the
majority of bacterial shapes:
1. Growth
2. Cytokinesis

6.  GROWTH
Growth can occur by PG synthesis evenly distributed throughout the cell
(dispersed growth) or from one or many spatially restricted zones, leading
to zonal growth . Zonal growth can be specified spatially by various
molecular mechanisms to yield different shapes
 CYTOKINESIS
Cytokinesis (often called septation in bacteria)Cell division requires directing
PG synthesis inwards, usually at the midcell, perpendicular to the long axis
of the cell. Cell division is mostly governed by the tubulin homolog FtsZ
which assembles into filaments to form a ring-like structure (Z-ring) around
the division plane. FtsZ recruits, directly or indirectly, a large number of
proteins involved in PG synthesis, as shown in various species

7. INDUCED BY
Hormones
Morphogenetic responses may be induced in organisms
by hormones
By environmental chemicals
Ranging from substances produced by other organisms to toxic
chemicals or radionuclides

8. DIFFERENTIATION
• Cellular differentiation is the process in which a cell changes from one
cell type to another. Usually, the cell changes to a more specialized type.
• Important reasons for differentiation
1. Adoption to environmental conditions.
2. Expressing different functions at different times in the life cycle

9. Endospore formation in Bacillus
subtilis

10. Endospore formation
• It is an extreme survival strategy employed by certain low G+C
Gram-positive bacteria.
• Spores are resistant to heat, cold, radiation, and other adverse
environmental conditions.
• The primary function of endospore formation appears to be the
survival and dissemination of the species.
• When the environment becomes more favorable, the endospore
can reactivate itself to the vegetative state

11. Endospore formation in Bacillus
subtilis
Actively growing cells of Bacillus subtilis are induced to
differentiate into spores by starvation for carbon, nitrogen or,
in some circumstances a phosphorus source

13. SPORULATION GENES
STAGE
GENE
DESIGNATION
FUNCTION
I. citC
Isocitrate
dehydrogenase
STAGE
GENE
DESIGNATION
FUNCTION
II spoOA
Regulates
phosphorelay
system

14. STAGE
GENE
DESIGNATION
FUNCTION
III
spoIIIA
spoVE
Prespore
engulfment
Cortex synthesis
STAGE
GENE
DESIGNATION
FUNCTION
IV
cotD
cotT
cotA
cotB
cotC
gerE
Coat synthesis
Coat synthesis
Coat synthesis
Coat synthesis
Coat synthesis
Germination

15. SPORE CORTEX

16. Heating (65-70°c for 30- 45 mins)
Low ph or low temparature
chemical agents
ACTIVATION

17. GERMINATION
Germination occurs in response to specific germinants that act as triggers.
Change in the structure and physology of spore includes
 Loss of heat resistance
 Ion fluxes
 Release of calcium ions
 Reduction in dipiclonic acid
 Hydrolysis of peptidoglycon
 Rehydration of core protopast
 Resumption of metabolic activity

18. GERMINATS
 L- alanine
 L-alanine plus inosine
 Sugar plus inorganic ions
 Inorganic ions
 Asparagine
 Glucose
 Fructose
 KCl

19. GERMINATION MONITORNING
• Loss of density
• Loss of heat resistence
• Change in apperance under phase contrast microscope
• Tetrazolium test

20. Out Growth
• Degradation of the cortex and outer layers results in emergance of a
new vegetative cell consisting of the spore protoplast eith its
surrounding wall.
• A period of active biosynthesis follows. This period, which
terminates in cell division. Is called out growth. The transition from
germinated spore to vegetative spore is also termed as our growth
• Outgrowth requires a supply of all nutrients essential for cell
growth.

21. CAULOBACTER DIFFERENTATION
The gram-negative bacterium Caulobacter provides another example in which
a cell divides into two genetically identical daughter cells that are
structurally distinct and perform different roles and express different sets of
genes. Caulobacter is a species of Proteobacteria that is common in aquatic
environments, typically in waters that are nutrient-poor (oligotrophic). In
the Caulobacter life cycle, free-swimming (swarmer) cells alternate with
cells that lack flagella and are attached to surfaces by a stalk with a holdfast
at its end. The role of the swarmer cells is dispersal, as swarmers cannot
divide or replicate their DNA. Conversely, the role of the stalked cell is
reproduction.

22. CAULOBACTER AS A MODEL FOR THE
EUKARYOTIC CELL CYCLE
Both external stimuli and internal factors such as nutrient and metabolite levels result in the
precise coordination of morphological and metabolic events within the Caulobacter cell
cycle. Since its genome has been sequenced and good genetic systems for gene transfer and
analysis are available, differentiation in Caulobacter has been used as a model system for
studying cell developmental processes in other organisms as well. This focus is due to the
strict cell cycle followed by Caulobacter, which resembles that of eukaryotic cells in many
respects. In fact, terminology used to describe the eukaryotic cell cycle has been adapted to
the Caulobacter system. In eukaryotic cells, phase G1 of cell division is where growth and
normal metabolic events occur while in phase G2 the cell prepares for subsequent mitotic
events, which occur in the M phase. Between G1 and G2 is the S phase, where DNA
replication occurs. In the Caulobacter life cycle there is no mitosis, of course, but analogs of
the G1, G2, and S phases are apparent and these make this bacterium an excellent model for
studying cell division events in higher organisms.