Priyanshi mishra (1)

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Dr. Harisingh gour central university sagar
(M.P)
Synchronous growth
Submitted to- Dr. Yogesh Bhargav (department of
applied microbiology)
Submitted by- Priyanshi mishra Msc. 2nd
semester
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• Introduction,
• Methods of obtaining
• synchronous culture,
• Selection by size and age,
• Selection by induction
• Technique.

Synopsis
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Synchronous growth

• Synchronous growth- Synchronous growth is the
  growth of bacteria such that all the bacteria are
  at the same stage in their growth cycle.
• All the cells in the culture will divide at the
  the same time, will grow for the
• generation time, and all will divide again at
  the same time.
• Thus, the entire population will kept under
  uniform with respect to the
• growth and division.
• Synchronous growth provides the entire cell crop
  in same stage of growth.
• Measurement made on such cultures are equivalent
  to the measurement
• made on individual cells.
• These culture is important in the study of
  genetics and metabolism.
• The easiest way to synchronise bacterial growth
  is to add some cytostatic
• agents so that cells dont divide and they all
  maintain the same state.
• When the cytostatic agent is removed all cells
  start to divide at the same
• time.

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Cont

• Synchronous culture is very useful, as it is
  practically
• impossible to study a single cell.
• Synchronous culture of bacteria can be obtained
  by a
• number of techniques. Two fundamentally different
  
• experimental approach have been employed.
• Selection by size and age,
• Selection by induction technique.

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Selection by size and age

• A population of cells is fractionated on the
  basis of size. Cells are filtered so that
  smallest cells pass through the filter.
• These small cells are the youngest and must go
  through their whole life
• cycle before dividing.
• Alternatively, the largest cells, which are ready
  to divide, may be retained
• or retarded by a filter.
• These are then collected separately and used to
  obtain synchronous
• culture.
• The most widely used method for obtaining
  synchronous cultur is the
• Helmstetter cummings technique.
• Instead of filtration, density gradient
  centrifugation is also used to
• separate the cells.

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Helmstetter cummings technique

• Helmstetter cummings technique in which an
  unsynchronised
• Bacterial culture is filtered through cellulose
  nitrate membrane filter.
• Loosely bound bacterial cells are washed from the
  filter, leaving some
• cells tightly associated with filter.
• Filter is now inverted and fresh medium is
  allowed to flow through it.
• New bacterial cells, that are produced by cell
  division and are not tightly
• associated with the filter, are washed into an
  effluent.
• All the cells in the effluent are newly formed
  and are, therefore, at the
• same stage of growth and division cycle.
• The effluent represents a synchronous culture.

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Helmstetter Cummings technique
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Selection by induction techniques

• A synchronous culture is also obtained by use of
  shock treatment.
• These include variation in temperature,
  starvation, exposure of light
• (for photosynthetic organisms), drugs and
  sublethal doses of radiation.
• A commonly used technique involves submiting a
  culture of microorganism to
• single or multiple changes in temperature.
• An exponentially growing culture at 37c is held
  for about 30 minutes at 20c.
• The lower temperature retards cell division.
  During the interval of 30 minutes all
• the cell mature to a point of fission.
• However, at 20c none divide on sudden return of
  the culture to 37c, all the cells
• divide synchronously.
• By repeating the alterations of temperature
  synchrony can be maintained in
• culture for several generations.
• The techniques based on selection are preferable
  to those based on induction,
• Since induction is likely to introduce
  distortions in the physiologic state of the cell.

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Thank you ??