Bacterial Growth and Metabolism Flashcards
Bacterial Growth
-Increase in size and numbers
-Use nutrients from the environment to synthesize new cellular components, such as ribosomes, nucleoid, cell wall and plasma membrane
-division with new daughter cells formed
How do bacteria grow?
-in a closed system where eventually nutrients are very limited because not its not an environment where you have nutrients constantly coming in.
-The classical growth curve has 4 phases
1) Lag phase: no increase in number of living bacterial cells (adaptation). Initial phase when bacteria are just beginning to enter that environment and grow.
2) Log phase: exponential increase in number of living bacterial cells. Rapid growth of bacteria.
3) Stationary phase: Plateau in number of living bacterial cells; rate of cell division and death roughly equal. “Survival”. Constant state. Growth and death of bacteria keeping rate steady.
4) Death or decline phase: Exponential decrease in number of living bacterial cells. Due to lack of nutrients, toxic products, etc.
Bacterial growth in laboratory
-in lab under favorable conditions, a growing population of bacteria doubles at regular intervals (exponential/ Log phase).
-Geometric growth: 1,2,4,8, etc. or 2^0, 2^1, 2^2,…. 2^n (where n = number of generations)
-Exponential growth is only one part of the bacterial life cycle and may not be representative of the normal pattern of bacterial growth in nature
-doubling (generation) time varies between bacterial species and conditions.
–> E. Coli: ~20 minutes in lab, 12 to 24 hr in intestinal tract (much slower process in nature)
–> T. denticola: ~ 12 hours in liquid broth, 26 hr in biofilm
Bacterial growth in real life in the oral cavity: biofilm
-in nature (in oral cavity and gut), bacteria grow in biofilms and do not grow at an exponential rate (acquire nutrients / survival)
–> bacteria well adapted to their environment
-in real life most of the organisms are in this stationary phase where they are trying to survive
