Bacteria reproduce asexually through binary fission or budding. In binary fission, a bacterium grows and its DNA replicates before the cell divides into two identical daughter cells. Bacteria can double in number as quickly as every 9.8 minutes under optimal conditions. Some bacteria reproduce through budding, where a small bud forms on the mother cell and eventually separates. Bacteria can also exchange genetic material through transformation, transduction, and conjugation, allowing for rapid adaptation.

1. Reproduction in
bacteria
By:
Mrs. Mali Dhanashri R.
Assistant professor,
GES’s Sir Dr. M. S. Gosavi College of Pharmaceutical
Education and Reseach

2. Reproduction
 Cell growth and reproduction by cell division are
tightly linked in unicellular organisms.
 Bacteria are prokaryotic organisms that reproduce
asexually.
 Bacteria grow to a fixed size and then reproduce
through 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.

3. Types of reproduction
Binary fission
Budding
Fragmentation
Formation of Conidiospores or
sporangiospores

4. Multiplication & divisional
cycle
 Many bacterial cell multiply by binary fusion.
 Means, each individual cell increase in size until it is large
enough to divide into two identical daughter cells.
 At that time of separation each daughter cell must be
capable of growth & reproduction.
 While each daughter cell will automatically contain mRNA,
rRNA, ribosomes, enzymes, cytochromes etc. from mother
cell.

5. Binary fission
 Most prokaryotes reproduce by a process of binary
fission
 In binary fission, 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.

6.  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.

7.  Binary fission begins with the single DNA
molecule replicating and both copies
attaching to the cell membrane.
 Next, the cell membrane begins to grow
between the two DNA molecules. Once the
bacterium just about doubles its original
size, the cell membrane begins to pinch
inward.
 A cell wall then forms between the two DNA
molecules dividing the original cell into two
identical daughter cells

9. 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
inbudding fungi, such as brewer’s yeast
(Saccharomyces cerevisiae).

10.  One difference between fission and budding
is that, in the latter, the mother cell often has
different properties from the offspring.
 Ex: In some strains, mother cells have a
flagellum and are motile, whereas the
daughter buds lack flagella.


12. Fragmentation
 Becteria may produce extensive filamentous
growth.
 It reproduce by fragmentation of fillaments into
small bacillary or coccoid cells.
 Each filament grows and forms new cells.
 E.g. Norcardia species.

13. Formation of Conidiospores
 Conidia formation takes place in filamentous
bacteria like Streptomyces etc., by the
formation of a transverse septum at the apex
of the filament
 The part of this filament which bears conidia
is called conidiophore.
 After detachment from the mother and
getting contact with suitable substratum, the
conidium germinates and gives rise to new
mycelium.

15. Growth & Genetic exchange
 For many years it was thought that bacteria, unable to
exchange genetic material and could only adapt and evolve
through mutation of genes.
 The bacteria has profound ability to exchange and share
DNA across diverse genera.
 This is of particular significance because it enables
bacterial populations to adapt rapidly to changes in their
environment,.
 This also help in the deployment of antibacterial chemicals
and antibiotics.
 Three major process involved in genetic exchange….
 Transformation
 Transduction
 Conjugation

16. Transformation
 Discovered by Frederick Griffith in 1928.
 The early work on the transfer of virulence in the
pathogen Streptococcus pneumoniae .
 The stage for the research that first showed that DNA
was the genetic material.
 Griffith found that if he boiled virulent bacteria and
injected them into mice, the mice were not affected
and no pneumococci could be recovered from the
animals.
 When he injected a combination of killed virulent
bacteria and a living nonvirulent strain, the mice died;
moreover, he could recover living virulent bacteria
from the dead mice.
 Griffith called this change of nonvirulent bacteria into
virulent pathogens transformation.

18.  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.

19. Transduction
 It is defined as a phenomenon causes
genetic recombination in bacteria wherein
DNA is carried from one specific bacterium
to another by a bacteriophage.
 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.

21.  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.

22.  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.
 As well as temperate phage will be active once
again at a low frequency & phasing between
temperate & lytic forms ensures the long-term
survival of the virus.

24. Conjugation
 Conjugation is a natural process
representing the early stages in a true
sexually reproductive process.
 In that transcribed to produce singular
viral elements, which cannot assemble
or lyse the host cell. Such DNA strand
are known as plasmids.
 Plasmids are circular & can either be
integrated into the main chromosome, in
which case they are replicated along
with chromosome & passed to daughter
cells or they are separate from it & can
replicate independently.
 The simplest form of plasmid is F-factor
(fertility factor).
 The cells containing an F-factor are
designed F+