Elements of Nutritional, Ecology, and Growth

1
Chapter 7

• Elements of Nutritional, Ecology, and Growth

2
Nutrients

• Needed for cell growth and metabolism
• Categories of essential nutrients
• Macronutrients-play a large role in cell
  structure and metabolism
• Include protein, carbohydrate, hydrogen,
  oxygen, carbon, phosphorus and sulfur
• Micronutrients-are needed in smaller quantities
  for enzyme function and in maintenance of protein
  structure and include trace elements like
  manganese, zinc, iron, copper, and nickel

3
Nutrients continued

• Also have inorganic materials like metals, gases,
  and water
• And finally organic materials include substances
  containing carbon and hydrogen and are usually
  the products of living things

4
Chemical analysis

• Bacteria are 70 water
• Protein is the next most abundant ingredient
• 6 essential elements make up the majority of the
  above (C, H, N, O, P, S)
• Nitrogen (14) and sulfur are necessary for
  protein synthesis
• Nitrogen and phosphorus are needed for DNA and
  RNA and ATP

5
Chemical requirements

• Besides water, one of the most important
  requirements for microbial growth is carbon
• Carbon is the structural backbone of living
  matter, it is needed for all the organic
  compounds that make up a living cell
• Half the dry weight of a cell is carbon

6
Metabolic Diversity according to nutritional
pattern

• Consider energy source first You have either
  phototrophs or chemotrophs
• Phototrophs use light as their energy source
• Chemotrophs use oxidation-reduction reactions of
  inorganic or organic compounds for energy

7
Principal carbon source

• Autotrophs use carbon dioxide as their primary
  carbon source and are called self-feeders
• Some autotrophs are called lithotrophs (rock
  eaters)
• Heterotrophs or organotrophs use organic carbon
  and feed on other living things (the word means
  other feeding)

8
Combinations

• Photoautotrophs-use light as energy source and
  carbon dioxide as carbon source
• Photoheterotrophs-use light as energy source but
  use organic compounds like alcohols, fatty acids,
  other organic acids, etc as primary carbon sources

9
Combinations

• Chemoautotrophs-use electons from reduced
  inorganic compounds as source of energy, and
  carbon dioxide as their carbon source
• Chemoheterotrophs-use same organic compound for
  energy source and carbon source
• ---Can subclassify these based on source of
  organic molecules (saprophytes use dead organic
  matter, parasites use living hosts)

10
Environmental influences

• Temperature adaptations minimum temperature is
  lowest temperature that permits growth
• Maximum temperature is the highest temperature
  that permits growth
• Optimum temperature is the best for growth

11
Temperature classifications

• Psychophiles-love cold 0-20 C (optimum is 15 C)
  found in ocean
• Psychrotrophs-survive in refrigerator (optimum
  20-30C). Many of your food poisoning cases are
  caused by these bacteria-Staphylococcus aureus
  for example

12
Temperature continued

• Mesophiles-middle range-10-50 C with optimum of
  25-40 C. Human pathogens fall in this category
• Thermophiles-love heat, range is 45-80 with
  optimum over 45C (Hot Springs, AR)
• Hyperthermophiles are members of Archeae and love
  80C or higher. These live in hot springs
  associated with volcano
• Notice there is overlap between groups.

13
Gas requirements

• Molecular oxygen is actually poisonous, but most
  organisms that use it have developed enzymes that
  neutralize it.
• Organisms that require oxygen to live are called
  obligate aerobes
• Facultative anaerobes can use oxygen if it is
  present but continue to grow if it is absent by
  using anaerobic respiration or fermentation

14
Gas Requirements

• Obligate anaerobes-cant use oxygen and are
  harmed by it.
• Toxic forms of oxygen include singlet oxygen
  (1O2-,) superoxide free radicals (O2-) peroxide
  anion, and hydroxyl radical (OH-)
• Aerotolerant anaerobes cant use oxygen for
  growth but tolerate it

15
Gas Requirements

• Capnophiles-require extra carbon dioxide
• Microaerophiles use low concentrations of oxgyen

16
pH requirements

• pH refers to the acidity of alkalinity of a
  solution
• Range is from 0-14 with acid being 0-6 and
  alkaline 8-14. Neutral is 7.
• Most bacteria grow best in a narrow range between
  6.5 and 7.5
• Acidophiles-can survive and prefer low pH
  (obligate prefer pH of 1 or 2)
• Molds prefer pH of 5-6

17
pH continued

• Alkalinophiles prefer 8-10 pH
• The majority of bacteria are neutrophiles and are
  in the middle
• Helicobacter pylori can metabolize urea and
  neutralize stomach acid, causes ulcers

18
Other classifications

• Halophiles-salt loving
• Facultative halophiles-0.1 to 20
  (Staphylococcus aureus)
• Obligate-prefer salt concentrations of 25 or
  more.
• Osmophiles can with stand high osmotic pressure
  due to sugar/salt concentrations (used to
  preserve foods)

19
Symbiosis

• Relationships between organisms
• Mutualism-both organisms benefit
• Commensalism-1 benefits, 1 isnt affected
• Parasitism-1 benefits, 1 is harmed
• Synergism-interrelationship between 2 or more
  organisms that is beneficial to both, but not
  necessary for their survival
• Antagonism-competition between species
• Antibiosis-production of antibiotic

20
Growth

• Bacteria reproduce by binary fission
• Usually takes about 20 minutes average doubling
  time, but varies depending on species
• Some take days or months
• Generation time is time required for a cell to
  divide and population to double

21
Growth curve

• Lag phase-adjustment period, no growth-may be
  several hours to several days
• Log phase-rapid growth, also called exponential
  growth, easier to kill bacteria in this phase
• Stationary-growth rate slows, metabolic activity
  slows, population stablizes
• Death or decline phase- of deaths exceeds of
  new cells formed

22
Growth curve

• The growth curve shows all 4 stages

23
Analysis of Growth

• Turbidity-use a spectrophotometer to estimate
• Direct or total cell count-use a coulter counter
  (electronic) scanner that can tell live from dead
  cells and automatically counts cells in a known
  volume of liquid
• Also can use a cytometer which is a special
  slide with grids for a direct cell count-usually
  use a 0.01 ml sample

24
Plate Counts

• Most frequently used method of measuring
  bacterial populations
• Measures viable cells, often reported as
  colony-forming units (CFU)
• Count plates containing 30-300 colonies
• Use serial dilutions to obtain that amount

25
Pour plate and spread plate

• Both used to do a plate count
• In pour plate, use a 1.0 ml or 0.1 ml dilution of
  bacterial suspension in the bottom of the plate
• Add liquid agar, agitate, let solidify, then
  incubate
• Spread plate uses 0.1 ml of inoculum on top of
  prepared agar plate and spread

26
Filtration

• Small amounts can be counted using filtration
  method
• 100 ml of water pass through thin membrane
  filter, bacteria are captured
• Filter transferred to petri dish, incubated,
  counted

27
Most Probable Number

• MPN is a statistical method based on the fact
  that the greater number of bacteria there are in
  a sample, the more dilution is needed to reduce
  density to a point where no bacteria are left to
  grow in the tubes in a serial dilution series
• It is a statement there is a 95 chance the
  population falls within a certain range