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#exponential growth

25 public questions tagged with this topic.

Animal Tissue Culture 3

Cell viability during log phase is approximately:

Exponential log phase represents period of maximal health for mammalian cultures. Under optimal conditions of adequate nutrients, pH maintained at 7.2-7.4 by CO2-bicarbonate buffering, temperature 37°C, and absence of waste accumulation, trypan blue exclusion tests reveal membrane intact viable cells at 90-100% because apoptotic signaling minimal, caspase-3 inactive, mitochondrial membrane potential high as indicated by JC-1 aggregation. Mitochondrial succinate dehydrogenase activity robust leading to efficient reduction of tetrazolium salts in MTT assay. Cells display high cloning efficiency

Ref: Freshney Ch.18 Viability during log 90-100%; ATCC Cell Viability trypan blue exclusion exponential phase near maximal.

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Microbial Physiology

Which equation best describes exponential bacterial growth?

Exponential increase in bacterial population when resources unlimited follows first order kinetics proportional to current population. Mathematically rate change dN over dt equals mu N, where N cell number, mu specific growth rate inverse time. Factor mu reflects nutritional quality, temperature, aeration, strain genotype. Integration yields N(t) equals N0 e to mu t, equivalently N0 2 to power t over g, where g equals ln2 over mu generation time. Taking natural logarithm ln N versus time gives straight line slope mu, confirming balanced growth. Monod equation refines mu as function substrate c

Ref: Prescott's Microbiology, 11th ed., Chapter 7: Exponential growth equation dN/dt=μN.

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Microbial Physiology

Which phase is characterized by exponential bacterial growth?

Log phase also termed exponential phase represents balanced growth state where every cellular constituent doubles at identical specific rate. Under saturating nutrients and aeration, DNA replication initiates synchronously via DnaA ATP activation at oriC, elongation by PolIII, segregation by MukBEF SMC complex, and cytokinetic ring FtsZ with FtsA ZipA divides cells with constant interdivision time. Specific growth rate mu maximal, defined by mu equals ln2 over generation time g. Equation dN over dt equals mu N integrated yields N equals N0 times e to mu t, producing straight line on semi-log p

Ref: Prescott's Microbiology, 11th ed., Chapter 7: Exponential phase and balanced growth.

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Microbial Physiology

Which equation best describes the exponential bacterial population growth?

Exponential growth is idealized as first-order autocatalytic process where instantaneous rate of new cell formation is proportional to existing population. Differential equation is dN/dt equals mu times N where N is cell number at time t and mu is specific growth rate per hour reflecting intrinsic replication speed. Separation and integration yields Nt equals N0 times e to power mu t giving linear relationship between ln Nt and time with slope mu during log phase representing balanced growth. During true log phase mu approximates constant as all components increase proportionally. Alternative

Ref: Madigan et al., Brock Biology of Microorganisms, 16th ed., Chapter 4: Exponential Growth Equation dn/dt = μN.

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Microbial Physiology

During the log phase, bacterial cells:

Logarithmic phase also termed exponential phase reflects balanced growth where all cellular constituents increase in constant proportion and cells divide at maximal specific rate mu max set by genotype and environment. Biomass, protein, RNA, DNA and numbers double at exact constant generation time. DNA replication precisely matches division rate, ribosome content peaks up to 70 percent dry weight, peptidoglycan precursor synthesis via Mur enzymes operates maximally, and transcription of glycolysis and TCA cycle remains high while alarmone ppGpp stays low. Plotting log colony forming units vers

Ref: Madigan et al., Brock Biology of Microorganisms, 16th ed., Chapter 4: Log Phase and Exponential Growth Dynamics.

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