Elements of Microbial Nutrition, Ecology and Growth

Chapter Overview:

• Microbes and their ability to survive in various habitats and the different environmental factors.
  
• Microbial nutrition, the sources of nutrients and nutritional types.
• Movement of chemicals, water, and solutes.
  

Microbial Nutrition

Nutrition

Nutrients that are acquired from the environment are used for growth and metabolism. All living things have an absolute requirement for these bio-elements that include: carbon, oxygen, hydrogen, phosphorus, potassium, nitrogen, sulfur, calcium, iron, sodium, chlorine, magnesium, and a few other elements to survive. Microbes do have significant variances when it comes to the source, chemical form, and the amount they will need.
stages in the normal growth curve

• a population of bacteria does not maintain its potential growth rate and does not double endlessly, because in most systems numerous factors prevent the cells from continously dividing at their maximum rate
• quantitative laboratory studies indicate that a population typically displays a predictable pattern, or growth curve over time
• method traditionally used to observe the population growth pattern is a viable count technique, in which the total number of live cells is counted over a given time period

Essential Nutrients:

Are any molecular or elemental form of nutrient that is required by an organism.

• Two categories of essential nutrients; macro-nutrients and micro-nutrients.
  • Macro-nutrients are needed in larger amounts.
    • Used to help with cell structure and the cell's metabolism.
    • Examples are proteins, and carbohydrates.
  • Micro-nutrients or trace elements are needed in a lot smaller amount.
    • They help enzyme function and help to maintain protein structure.
    • They include elements such as zinc, manganese, and nickel.

THE SOURCE OF COMMON ESSENTIAL NUTRIENTS ARE: CHNOPS

• Carbon
• Hydrogen
• Nitrogen
• Oxygen
• Phosphorous
• Sulfur

Carbon Content Nutrients:

Carbon content is another way that nurtients are categorized. Sources of nutrients is extremely varied and some microbes will obtain their nutrients entirely from inorganic sources and others require a combination of organic and inorganic sources.

• Organic nutrients:
  • Contain at least some combination of carbon and hydrogen atoms.
  • Natural organic molecules are usually products of livings things.
  • Simple to large polymers.
• Inorganic Nutrients:
  • An element or simple molecule that contains elements other than carbon and hydrogen.
  • Natural reservoirs are mineral deposits in the crust of the earth, bodies of water and the atmosphere.

EX: metals and their salts (magnesium, sulfate, ferric nitrate, sodium phosphate).

EX: Gases (oxygen, carbon dioxide) and water

REMEMBER!! In order for it to be an organic molecule or nutrient it has to have both carbon and hydrogen, and it can be a combination of any other element, just as long as it has both.


Carbon Sources

Even though there is a distinction between the types of carbon cells can absorb as nutrients. It is important to know that the majority of carbon involved in the structure and metabolism of all cells are organic

• Heterotrophs: Organisms that must obtain it's carbon in an organic form, because of organic carbon originate from the bodies of other organisms

-that's you, me, all other animals, and many microbes
-when you obtain carbon from a protein or carbohydrate, you are getting other nutrients along with it.
-Not all forms of organic carbon are available to all species (most things cannot digest cellulose, for example.
-heterotrophs are dependent on other life forms.
-Common organic molecules that satisfy heterotrophs requirements are carbohydrates, proteins, lipids, and nucleic acids.
-Some organic nutrients available to heterotrophs already exist in a form that is simple enough for absorption (monosaccharides, amino acids)
-Many larger molecules must be digested by the cell before absorption.
-not all heterotrophs can use the same carbon sources, some are restricted to a few substrates, whereas others (certain pseudomonas bacteria, for example) are so versatile that they can metabolize more than 100 different substrates.

• Autotrophs: Organisms that uses CO2 (an inorganic gas) as its carbon source.

-Because autotrophs have the special capacity to convert CO2 into organic compounds they are not dependent on other livings things and are considered self-sustaining.
-Plants and photosynthetic microbes (and chemoautotrophic microbes too)
-These organisms form the base of the food chain that all other life depends on
- Even though they obtain carbon in a different manner, they use it in basically the same way as heterotrophs
- Examples of autotrophs are plants and photosynthetic microbes.

Chemoautotrphs: these organism requires neither sunlight nor organic nutrients

Q: Which of the following defines a Heterotroph?
a. An organism that must obtain its carbon in an organic form
b. An organism that does not require essential nutrients for growth
c. An organism that produces all the trace elements it requires for growth
A: An organism that must obtain its carbon in an organic form

Q: Molecules that satisfy heterotophic nutritional requirements include all but which of the following?
a. Water
b. Lipids
c. Proteins
A: Water


Q:The primary sources of nitrogen for heterotrophs include all except which of the following?
a. Glucose
b. RNA
c. Amino Acids
A: Glucose

Nitrogen Sources:


-Main reservoir of Nitrogen (N2)
-79% of earth's atmosphere is N2
_Nitrogen is part of the structure of protein, DNA, RNA, & ATP.
-Such compounds are the primary Nitrogen source for heterotrophs, but to be useful, they must first be degraded into their basic building blocks (proteins into amino acids; nucleic acids into necleotides
- Some bacteria/algae utilize inorganic Nitrogenous nutrients such as Nitrate (NO3), nitrite (NO2), or Ammonia (NH3).
- In procaryotes a small number can change N2 (nitrogen gas) into compounds usable by other organisms through the process of Nitrogen fixation
- Regardless of the initial form in which the inorganic Nitrogen enters the cell, it must first be converted to NH3, the only form that can be directly combined with Carbon to synthesize amino acids and other compounds the Nitrogen into usable pieces for other organisms to use.

Oxygen Sources:
-Because oxygen is a major component of organic compounds such as carbohydrates, lipids, nucleic acids, and proteins, it plays an important role in the structural and enzymatic functions of the cell. Oxygen is likewise a common component of inorganic salts such as sulfates, phosphates, nitrates, and water. Free gaseous oxygen (O2) makes up 20% of the atmosphere. It is absolutely essential to the metabolism of many organisms.

Hydrogen Sources:

Major element in all organic and several inorganic compounds such as water, salts, hydrogen, sulfide, methane, and hydrogen gas. (used/produced by microbes) Essential in biochemistry of cells:
*form hydrogen bonds (oxygen/nitrogen)
*free energy in reactions of respiration
*maintain pH of solutions

Phosphate Sources:

Found in rocks and oceanic mineral deposits. Key component of nucleic acids which makes it essential to the genetics of cells/viruses. Serves in cellular energy transfers (found in ATP). Some compounds are phospholipids (cell membrane) or co-enzymes. Lack of phosphate will limit the ability for some organisms to grow.


Sulfur Sources:

Found widely throughout the environment in mineral form. Essential component for some vitamins (B1) and the amino acids (which help determine shape/structural stability of proteins) methionine and cysteine. Rocks and sediments can contain sulfate, sulfides, hydrogen sulfide gas, and elemental sulfur.

PABA (Para-AminoBenzoic Acid)
Was once a key component in sun screen. Similar to Folic Acid. Stopped adding it to sunscreen when they realized that it was more important to bacteria then for us. Problems with Sulfa drugs not working.

Other Important Nutrients:
The rest of the elements that are used in microbial nutrition are called mineral ions. Potassium is needed for protein synthesis and membrane function. Sodium is used for cell transport throughout the organism. Calcium stabilizes the cell wall and bacterial endospores. Magnesium works with chlorophyll and helps to stabilize membranes and ribosomes. Iron is an important part of the cytochrome pigments for cell respiration.

Key Terms:
Nutrition- nutrients are acquired from the environment and used for cell metabolism and growth.
Macro-nutrients- needed in large amounts to help with metabolism and cell structure (proteins, carbs).
Micro-nutrients-trace elements in small amounts used for enzyme function and maintaining protein
structure (manganese, nickel, zinc).
Inorganic nutrient- an atom or simple molecule that has a combination of atoms not including carbon
and hydrogen.

Transport Processes in Cell:
Passive: Energy expenditure is not required. Substances exist in a gradient and move from areas of higher concentration towards areas of lower concentration in the gradient.

• Diffusion: A fundamental property of atoms and molecules that exist in a state of random motion
  • Qualities: Nonspecific Brownian movement
• Osmosis: Diffusion of water molecules across a membrane barrier that is freely permeable to water but selectively permeable to other molecule
  • Qualities: Direction depends on osmolarity of cell vs. habitat
• Facilitated diffusion: Molecule binds to a receptor in membrane and is carried across to other side
  • Qualities: Molecule specific; transports both ways

Active: Energy expenditure is required. Molecule need not exist in a gradient. Rate of transport is increased. Transport may occur against a concentration gradient.

• Carrier-mediated active transport: Atoms or molecules are pumped into or out of the cell by specialized receptors. Driven by ATP.
  • Qualities: Transports simple sugars, amino acids, inorganic ions (Na+,K+)
• Group translocaton: Molecule is moved across membrane and simultaneously converted to a metabolically useful substance.
  • Qualities: Alternate system for transporting nutrients (sugars, amino acids)

Bulk transport: Mass transport of large particles, cells, and liquids by engulfment and vesicle formation

• Qualities: Includes endocytosis, exocytosis, phagocytosis

Environmental Factor that influence Microbes:
Niche- totality of adaptations organisms make to their habitat.

Adaptation to Temperature: Microbial cells are unable to control their temperature and therefore assume
the ambient temperature of their natural habitats.
They have a Minimum Temperature, Maximum Temperature, and an Optimal Temperature.
Psychrophile: a microorganism that has an optimum temperature blow 15 degrees Celcius and is
capable of growth a O degrees celius.
Mesophiles: grow at intermediate temperatures.
Thermophiles: grows optimally at temperatures greater than 45 degrees Celcius.

Gas Requirements: Atmospheric gases that most affect microbial growth are oxygen and carbon dioxide.
Processing oxygen: as oxygen enters into cellular reactions, it is transformed into several toxins.
To protect themselves from damage, most cells have developed enzymes that go about the business of
scavenging and neutralizing these toxins.
Aerobe- an aerobic organism can use oxygen in its metabolism and possesses the enzymes
needed to process toxic oxygen products.
obligate aerobes cannot grow without oxygen.
facultative anaerobe- is an aerobe that doesn't require oxygen for its metabolism and is
capable of growth in the absence of it.
microaerophile- doesn't grow at normal atmospheric concentrations of oxygen but requires
a small amount of it in metabolism.
Anaerobe- Lacks the metabolic enzyme systems for using oxygen in respiration.

pH effects:
The majority of organisms live or grow in habitats between pH 6 and 8 because strong acids and bases can be
highly damaging to enzymes and other cellular substances.

Osmotic Pressure:
Most microbes exist under hypotonic or isotonic conditions. Osmophiles live in habitats with a high solute
concentration.
An osmotolerant microbe can adapt to a wide concentration in solutes.

Isotonic: no net movement of water
Hypotonic: Water moves into the cell and may cause the cell to burst if the wall is weak or damaged. Has lower osmotic pressure / soluet.
Hypertonic: Water moves oout of the cell, casuing it's cytoplasm to shrink. Has higher osmotic pressure / solute.

Microbial Interactions
Microbes coexist in many different relationships in nature.
1). Symbiosis or (mutualism) is reciprocal, obligatory,and a beneficial relationship between two organisms.
a. Commensalism: is an organism receiving benefits from another organism without harming the other organism its benefiting from.
An example is Satellitism
b. Parasitism: occurs between the host and an infectious agent.
2).Synergism: mutually beneficial to microbes bot not obligatory coexistence.
3). Antagonism: Microbes have competition, inhibition, and have directed injury against the opposing organism.
An example would be antibiotic production.


Flash cards for this chapter are on www.flashcardexchange.com under Kevin Young's Micro chapter 7

Questions:

Q&A Page~~Home Page~~Top of Page

1. True or False: Heterotrophs get their energy from sunlight and simple inorganic chemicals.

2 A pathogen would most accurately be described as a?
a. parasite
b. commensal
c. saprobe
d. symbiont

3 All of these are influential to microbes except_________.
a. temperature
b. oxygen requirements
c. osmotic pressure
d. b & c
e. all of the above

4.Extremophiles are most commonly what type of microorganism?
a. Algae
b. Protozoa
c. Yeasts
d. Archaea
e. Molds

5. Substances required by living organisms in relatively large quantities and which play principle roles in cell structure and metabolism are known as what?
a. Nutrients
b. Macro-nutrients
c. Micro-nutrients
e. Trace elements
f. Reservoirs

6. Nitrogen is required for the production of what category of molecules?
a. Fatty acids
b. Phospholipids
c. Nucleotides
d. Carbohydrates
e. Cellulose

7. Sugars can be transported into cells against their concentration gradient because of
a. osmosis
b. simple diffusion
c. facilitated diffusion
d. antiport with Na+
e. symport with Na+

8. Most bacteria grow between pH _______ and _________.
a. 1, 2
b. 5, 6
c. 5.5-6.6
d. 6.5-7.5

9. Molds and yeasts grow between pH ______ and ________
a. 6.5- 7.5
b. 5.5- 6.5
c. 5-6
d. 6-7

10. The main determinants of a microbes nutritional type are sources of what?
a. oxygen
b. oxygen and carbon
c. carbon and energy
d. nitrogen and carbon
e. all the above

11. What is not true about photoautotrophs?
a. they are photosynthetic
b. they convert inorganic carbon (CO2) into organic molecules that can be used be themselves and heterotrophs
c. they produce methane (CH4) from hydrogen gas and carbon dioxide
d. They capture the energy of light rays and transform it into chemical energy.
e. all of them are true

12. What is not true about parasites?
1. they live in or on the body of the host, which they harm to some degree
2. The more successful parasites strive for fatal effects
3. they cause damage to tissue (disease) or even death
4. Intracellular parasites are the most extreme

13. In order to be an organic molecule or nutrient you must have
A. Carbon
B. Nitrogen
C. Hydrogen
D. Both Carbon & Hydrogen

14. What type of organism could grow and thrive in South pole at zero degrees Celsius?
a. Mesophiles
b. Psychrophiles
c.Thermophiles
d. both A and B