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Bacterial growth

Bacterial growth. MUDr. Lenka Černohorská, Ph.D. Generation time (GT). G T = duration of the growth cycle = duplication time = time of doubling the number of bacteria G T of bacteria: on average 30 min Escherichia coli under ideal conditions 20 min Mycobacterium tuberculosis

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Bacterial growth

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  1. Bacterial growth MUDr. Lenka Černohorská, Ph.D.

  2. Generation time(GT) GT= duration of the growth cycle = duplication time = time of doubling the number of bacteria GT of bacteria: on average 30 min Escherichiacoli under ideal conditions 20 min Mycobacterium tuberculosis approximately 24 hrs

  3. Growth cycle of bacteria Bacteria reproduce by binary fission • Period I (iniciation): the cell grows, inside it proteins iniciating the next step accumulate • Period C (chromosome replication): it diverges from one spot in both directions opposite one another • Period D (division): • supply of macromolecules is created • cytoplasmic membrane inserts between the replicated chromosomes and separates them • cell wall grows into the cell and forms septum that divides the maternal cell into 2 daughter cells

  4. Microbial growth curve -Closed System stationary phase 10 8 logarithmic (exponential) phase 6 log number of viable cells death phase 4 2 lag phase approximately 24 hrs time

  5. Microbial growth curve shows the number of viable cells in the logarithmic scale, depending on the age of culture The result: 109 cells/24 hrs inthe stationary culture (in which nutrients are consumed and products of metabolism accumulate)

  6. Microbial growth curve – II Lag phase:microbes grow, but do not divide Logarithmic phase:cells divide with a constant speed (GT is constant); relation between the number of the living cells and the time isexponential Stationary phase:the number of cells is stable Death phase:sometimes it proceeds according to the exponential curve

  7. Division and arrangement of bacteria Cocci, in one plane:streptococci Cocci, in different planes:staphylococci Rods: • transverse division:majority (chain of rods) • lengthwise division:mycobacteria • corynebacteria: (palisade arrangement)

  8. Continuous culture The culture is continually supplied with nutrients and simultaneously disposed of the products of metabolism as well as the reproduced cells Culture vessels are called fermentors - are used in industry for the production ofmicrobial mass/for the production of various substances (antibiotics etc.) nutrients fermentor products cells

  9. Facts and cultivation If the generation time is 30 min, 1 cell produces after 24 hrs theoretically: 248 = 2.8×1014 cells, actually it is by 5 orders less (i.e. around 109 cells) 109 bacteria- an amount that is visible by the naked eye: It is used in cultivation: we use liquid or solid media, where we can see the typical „changes“ of medium made by various bacteria (time of cultivation depends on GT of bacteria)

  10. Liquid medium (broth) Possible changes: • becomes cloudy • pellicle appears at the top • sediment appears at the bottom Various liquid broths: TSB, BHI,VL-broth, selenite-broth, broth…

  11. Solid medium (agar) Result: bacteria form colonies, some characteristics of colony: • colour • shape • opacity (translucency) • profile • odour • margine (edge) • size • consistency • surface • surroundings (hemolysis)

  12. Solid media • basic – for most of bacteria (blood agar) • selective – selection of 1 bacterium (10% NACL – staphylococci) • diagnostic – some kind of bacteria can typically change the medium (MIU to MIU) • selective-diagnostic - mixture of previous (ENDO - selective for G-bacteria, diagnostic L+ or L-)

  13. Important solid media • for bacterial growth: Blood agar, Chocolate agar,Endo, MCs, XLD, MAL,Slanetz-Bartley,Sabourad agar,Löwenstein-Jennsen, 10%NACL, Levinthal agar, VL agar (VLA - anaerobes)… • for ATB testing - MH, MH with blood • for diagnostic procedures - MIU, Hajn… • for tranport – Amies, Stuart… • for longterm storage of cultures (glycerol serum broth)

  14. Important agars Blood agar Chocolate agar EndoXLD,MALSlanetz-Bartley 10%NACL Levinthal agar VL agarMH Hajn Sabourad agar Löwenstein-Jennsen

  15. Inoculation of the agar plate Isolated clear colonies – these are used for the susceptibility testing, biochemistry identification etc. 1 2 1, 2, 3, 4 – sterile bacterial loops used for the inoculation 3 4

  16. Blood agar with E. coli after 24 h incubation via 37 ºC

  17. Thank you for your attention

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