Prokaryotic Growth

1. ProkaryoticGrowth Kathy Huschle Northland Community & Technical College

2. Pure Cultures • pure culture: population of organisms descended from one organism • only approximately 1% of all bacteria can be cultured successfully in the lab Vibro chlorae

3. Pure Culture • colony, clone • begins with a single bacterial cell placed on a solid medium such as agar • agar • provides specific nutrition for bacteria and a medium to grow on Colonies on agar Nutritional Agar

4. Binary Fission • method of bacterial reproduction • cell divides exactly in half • single cell division • reproduction of the entire organism

5. Binary Fission • asexual • no genetic recombination • the DNA molecule replicates itself when bacterial reproduction takes place E. coli undergoing cell division

6. Bacterial Growth • bacterial growth = bacterial cell reproduction • the process of binary fission doubles the population each time binary fission takes place • this doubling time demonstrates exponential growth • each generation results in a doubling of the population generation time is = to doubling time • measure of microbial growth rate

7. Bacterial Growth Curve:laboratory conditions • bacterial growth generally follows a characteristic pattern • 5 phases • normal growth curve, with optimum environmental and nutritional conditions

8. Bacterial Growth Curve:laboratory conditions • lag phase • no increase in cell numbers • cells are adapting to the environment • cells are preparing for reproduction • synthesizing new DNA, etc.

9. Bacterial Growth Curve:laboratory conditions • log phase • exponential phase • maximal rate for reproduction • this happens with a specific set of growth conditions • those resources for growth are abundantly available

10. Bacterial Growth Curve:laboratory conditions • stationary growth phase • maximum population for the resources available • required nutrients become depleted • inhibitory end products from cell metabolism accumulate • cell growth = cell death

11. Bacterial Growth Curve:laboratory conditions • death phase • cell death > new cell formation

12. Bacterial Growth Curve:laboratory conditions • phase of prolonged decline • can last from months to years • “survival of the fittest”

13. Solid Media • on solid media • cells do not disperse readily • nutrients become limited in center • death phase occurs in the center with exponential phase at periphery of the bacterial colony

14. Bacterial Growth • most lab organisms are grown in a batch culture • closed system • new materials are not added • waste products are not removed • under these conditions bacteria populations follow distinct patterns of growth Algae batch cultures

15. Bacterial Growth • continuous culture maintained • nutrients must be continually supplied • end products must be removed • exponential growth phase maintained Continuous culture in lab

16. Natural Chemostat • chemostat • continuous culture device A cow, with it’s four stomachs, is natures perfect chemostat; constantly grazing to add nutrients and continually belching and other such mechanics to remove bacterial metabolic end products

17. Environmental Parameters:influencing bacterial growth • not all bacteria favor the same environmental conditions • the effects of varying conditions are seen as differences in reproduction (bacterial growth) • some environmental conditions that can affect bacterial growth include • temperature • oxygen • salinity • pH

18. Environmental Influencing Factors:temperature • temperature • ideal temperature for growth varies between organisms • specified by the bacterial genome

19. Environmental Influencing Factors:temperature • temperature growth range • minimum to maximum temperatures for bacterial growth • optimal growth temperature • temperature at which the highest rate of reproduction occurs

20. Environmental Influencing Factors:temperature • 5 divisions of prokaryotes, based on optimal growth temperature • psychrophiles • psychrotrophs • mesophiles • thermophiles • hyperthemophiles Psychrophile: Desulfofaba gelida Thermophile: Pyrococcus sp. Hyperthermophile: Thermococcus barophilus

21. Environmental Influencing Factors:temperature • psychrophiles • optimum growth temperature: -50C – 150C • found in the Arctic and Antarctic regions of the world Bacteria found in melt from a Russian outpost on Lake Vostok Desulfofrigus oceanense

22. Environmental Influencing Factors:temperature • psychotrophs • optimum growth temperature: 200C – 300C • will grow at lower temperatures • most commonly found in refrigerated food spoilage Stemphlium sarcinaeforme

23. Environmental Influencing Factors:temperature • mesophiles • optimum growth temperature: 250C – 450C • most human pathogens are mesophiles • adapted well to growth in the human body, whose normal temperature is around 370C Salmonella

24. Environmental Influencing Factors:temperature • thermophiles • optimum temperature: 450C – 700C • commonly found in compost heaps and hot springs, water heaters Sulfolobus Thermophile in a hot spring Sulfur pots in Yellowstone

25. Environmental Influencing Factors:temperature • hyperthermophiles • optimum growth temperature: 700C – 1100C • usually member of the Archae domain • found in hydrothermal vents in the depths of the ocean Deep Sea Vent

26. Temperature Ranges • psychrophiles • -50 C to 150 C • psychotrophs • 200 C to 300 C • mesophiles • 250 C to 450 C • thermophile • 450 C to 700 C • hyperthermophiles • 700 C to 1100 C

27. Temperature Considerations • food preservation • refrigeration • inhibits fast growing mesophiles • psychrophiles can still grow in refrigeration, but at a diminished rate • freezing destroys microorganisms that require water to grow

28. Temperature Considerations • disease • body temperature varies: extremities are usually cooler than 370C • some microorganisms can cause disease in certain body parts but not in others due to variations in body temperatures

29. Environmental Influencing Factors: oxygen • oxygen levels vary between environments and within the same environment • based on O2 requirements, prokaryotes are separated into the following groups • obligate aerobes • obligate anaerobes • facultative anaerobes • microaerophiles • aerotolerant anaerobes

30. Environmental Influencing Factors: oxygen • obligate aerobes • need oxygen present to multiply Giardia

31. Environmental Influencing Factors: oxygen • obligate anaerobes • cannot multiply in the presence of oxygen • often killed by traces of oxygen in their environment C. perfringens

32. Environmental Influencing Factors: oxygen • facultative anaerobes • grow best with oxygen, but can grow without oxygen • respiration if oxygen is available • fermentation if no oxygen is present • growth is greater in the presence of oxygen due to the production of more ATP (energy source of the cell) Aeromonas hydrophilia on intestinal cells

33. Environmental Influencing Factors: oxygen • microaerophiles • require oxygen but have maximal growth at reduced oxygen concentration • high concentration of oxygen inhibit growth Helicobacter sp. Helicobacter sp.

34. Environmental Influencing Factors: oxygen • aerotolerant anaerobes • indifferent to oxygen S. mutans

35. Environmental Influencing Factors: pH • based on pH of the environment, microorganisms are separated into the following groups • neutrophiles • acidophiles • alkalophiles

36. Environmental Influencing Factors: pH • neutrophiles • optimum pH of 7 (neutral) • most microorganisms grow best between pH of 5 (acidic) and pH of 8 (alkaline) • acidophiles • optimal growth, pH of less than 5.5 • alkalophiles • optimum pH of 8.5 or greater Copper Urinary bacterial infection caused by alkaline urine Copper tolerant acidophile

37. Environmental Influencing Factors: salinity • H2O is required by all microorganisms for growth • in some places H2O is hard to come by such as in salt concentrations • if a cell is in an environment that has a greater solute concentration than the interior of the cell, then by osmosis the water will leave the cell causing plasmolysis (shrinking of the cell)

38. Environmental Influencing Factors: salinity • halophiles are microorganisms that have adapted to this kind of environment • halophiles • require high levels of sodium chloride • moderate halophiles • 3% salt concentration • extreme halophiles: Archaea • require at least 9% salt solution • found in the Dead Sea Dunaliella salina cell, near a salt crystal. 40X Dead Sea

39. Nutritional Influencing Factors • major elements • C, O, H, N, S, P, K, MG, Ca Fe • essential components of protein, carbohydrates, lipids and nucleic acid • needed to synthesize cell components

40. Nutritional/Energy Influencing Factors • heterotrophs • utilize organic carbon • autotroph • utilize inorganic carbon • phototrophs • harvest the energy of sunlight • chemotroph • obtain energy by metabolizing chemical compounds Dinoflagellates Myxobacteria Purple Sulfur Bacteria: a chemotroph

41. Nutritional Diversity • prokaryotes are able to use diverse sources of carbon (an essential element) and energy • this ability allows them to thrive in virtually and environment Forms of Carbon

42. Nutritional Diversity • photoautotrophs • utilize the energy of sunlight • obtain carbon from CO2 • primary producers of the microbial world 6CO2 + 12H2O C6H12O6 + 6H2O + 6O2 • photoheterotrophs • utilize the energy of sunlight • obtain carbon from organic compounds Cyanobacteria Rhodobacter sphaeroides

43. Nutritional Diversity • chemolithoautotrophs • AKA as • chemoautotrophs or chemolithotrophs • energy from inorganic compounds such as hydrogen sulfide • carbon from CO2 Thiobacillus denitrificans

44. Nutritional Diversity • chemoorganoheterotrophs • AKA • chemoheterotrophs or chemoorganotrophs • utilize organic compounds for energy and as a carbon source • most common group of microorganisms associated with humans and animals • important organic degraders Brachionus calyciflorus B. vietnamiensis

45. Prokaryotes in the Lab • studying microorganisms in their environment, enhances our ability to grow them in the lab • lab growth is important for the study of the microbial world and its effect on human life

46. Lab Cultivation of Microbes • complex media • used for routine purposes • variety of ingredients needed by the microorganism are included in the media • nutrient agar, blood agar, PEA agar, Mannitol Salt agar are some examples S. aureus on blood agar

47. Lab Cultivation of Microbes • selective media • formulated with ingredients that inhibit the growth of some bacteria, such as an antibiotic, but enhance growth of the target organism • ie: MacConkey agar can be used to isolate Gram-negative rods

48. Lab Cultivation of Microbes • differential media • includes ingredients, such as chemical indicators, that produce observable differences between species of bacteria • ie: ph indicator may be incorporated with the agar medium allowing for the detection of acid producing microorganisms mannitol salt agar: pH indicator turns the agar yellow in the presence of a salt tolerant organism

49. Creating Appropriate Environmental Conditions • to enhance microbial growth in a lab, certain environmental conditions need to be created • atmospheric pressure • temperature • oxygen availability

50. Creating Appropriate Environmental Conditions • atmosphere • increase CO2 for some species of microbes Candle jar used in lab to increase CO2 concentration