Environmental Factors that Influence Microbial Growth

As a group, prokaryotes inhabit nearly every environment on earth. Many live in habitats that humans consider quite com-

Psychrophile Characteristics

Figure 4.4 Temperature Requirements for Growth Prokaryotes are commonly divided into five groups based on their optimum growth temperatures.This graph depicts the typical temperature ranges of these groups. Note that the optimum temperature, the point at which the growth rate is highest, is near the upper limit of the range.

Figure 4.4 Temperature Requirements for Growth Prokaryotes are commonly divided into five groups based on their optimum growth temperatures.This graph depicts the typical temperature ranges of these groups. Note that the optimum temperature, the point at which the growth rate is highest, is near the upper limit of the range.

4.3 Environmental Factors that Influence Microbial Growth 87

Table 4.1 Environmental Factors that Influence Microbial Growth

Environmental Factor/ Descriptive Terms

Characteristics

Temperature

Psychrophile Psychrotroph Mesophile Thermophile Hyperthermophile Oxygen (O2) Availability

Obligate aerobe

Obligate anaerobe

Facultative anaerobe

Microaerophile

Aerotolerant anaerobe (obligate fermenter)

Neutrophile Acidophile Alkalophile Water Availability

Osmotolerant Halophile

Thermostability appears to be due to protein structure. Optimum temperature between -5°C and 15°C.

Optimum temperature between 20°C and 30°C, but grows well at lower temperatures. Optimum temperature between 25°C and 45°C. Optimum temperature between 45°C and 70°C. Optimum temperature between 70°C and 110°C.

Oxygen (O2) requirement/tolerance reflects the organism's energy-converting mechanisms (aerobic respiration, anaerobic respiration, and fermentation) and its ability to detoxify O2 derivatives.

Requires O2.

Cannot multiply in the presence of O2.

Grows best if O2 is present, but can also grow without it.

Requires small amounts of O2, but higher concentrations are inhibitory.

Prokaryotes that live in pH extremes appear to maintain a near neutral internal pH by pumping protons out of the cell. Multiplies in the range of pH 5 to 8. Grows optimally at a pH below 5.5. Grows optimally at a pH above 8.5.

Prokaryotes that can grow in high solute solutions increase their internal solute concentration by either pumping ions into the cell or synthesizing certain small organic compounds.

Can grow in relatively high salt solutions, up to approximately 10% NaCl.

Requires high levels of sodium chloride.

Indifferent to O2.

environments as the Arctic and Antarctic regions and in lakes fed by glaciers.

■ Psychrotrophs have a temperature optimum between 20°C and 30°C, but grow well at lower temperatures. They are an important cause of food spoilage. ■ food spoilage, p. 811

■ Mesophiles, which include E. coli and most other common bacteria, have their optimum temperature between 25°C and about 45°C. Disease-causing bacteria, which are adapted to growth in the human body, typically have an optimum between 35°C and 40°C. Mesophiles that inhabit soil, a colder environment, generally have a lower optimum, close to 30°C.

■ Thermophiles have an optimum temperature between 45°C and 70°C. These organisms commonly occur in hot springs and compost heaps. They also are found in artificially created thermal environments such as water heaters and nuclear power plant cooling towers.

■ Hyperthermophiles have an optimum growth temperature between 70°C and 110°C. These are usually members of the Archaea. One member, isolated from the wall of a hydrothermal vent at an ocean depth of 3,650 meters, has a maximum growth temperature of 113°C, the highest yet recorded.

Why can some prokaryotes withstand such high temperatures but most cannot? As a general rule, proteins from thermophiles are not denatured at high temperatures. This thermostability is due to the sequence of the amino acids in the protein. These control the number and position of the bonds that form within the protein, which in turn determines its three-dimensional structure. For example, the formation of many covalent bonds, as well as many hydrogen and other weak bonds, prevents denaturation of proteins. Heat-stable proteins, which include enzymes that degrade fats and other proteins, are being used in high-temperature detergents. ■ protein denaturation, p. 29

88 Chapter 4 Dynamics of Prokaryotic Growth

Table 4.2 Oxygen (O2) Requirements of Prokaryotes

Obligate aerobe

Facultative anaerobe

Obligate anaerobe

Microaerophile s.'-"

Enzymes in Cells for O2 Detoxification

Catalase: 2H2O2 2H2O + O2 Superoxide dismutase: 2O2- + 2H+—> O2 + H2O2

Catalase, superoxide dismutase

Neither catalase nor superoxide dismutase in most

Small amounts of catalase and superoxide dismutase

Superoxide dismutase

How To Bolster Your Immune System

How To Bolster Your Immune System

All Natural Immune Boosters Proven To Fight Infection, Disease And More. Discover A Natural, Safe Effective Way To Boost Your Immune System Using Ingredients From Your Kitchen Cupboard. The only common sense, no holds barred guide to hit the market today no gimmicks, no pills, just old fashioned common sense remedies to cure colds, influenza, viral infections and more.

Get My Free Audio Book


Responses

  • milly
    What are the environmental factors that influence microbial growth?
    3 years ago
  • akseli
    What are the environmental factors that influence bacterial growth?
    3 years ago
  • niklas
    What are the the environmental factors that influence microbes?
    2 years ago
  • rudibert
    What are the environmental factor that influence micrbes?
    2 years ago
  • sandra
    How enviroment affects bacterial growth?
    2 years ago
  • nicole
    What are the environmental factors affecting microbial growth?
    2 years ago
  • ferumbras
    What are the environmental factors that limit microbial growth?
    2 years ago
  • moshe thomas
    What is the environmental factors that influence the growth of microorganism?
    2 years ago
  • Segan
    What can influence microorganism in an envuronment?
    2 years ago
  • Islay
    What are the environmental factors affecting micro organism?
    2 years ago
  • Gaudenzia
    What are you environmentally my factor influence the growth microorganisms?
    2 years ago
  • lorenzo
    What is environmental factors that influence the micro organism?
    2 years ago
  • madihah
    How can environmental factors play pivotal role in influencing in the growth of microorganisms?
    2 years ago
  • bilbo bracegirdle
    What are the factor factor that influence microbial growth?
    2 years ago
  • anna
    What are the influence of environmental factor microbiial activitie?
    1 year ago
  • aamos
    What are the ph environmenta factor affecting the presence of soil micro organism?
    1 year ago
  • Katy
    What are the factor that influence microbial activity?
    1 year ago
  • marie schulz
    What are the determinant of microbial growth?
    1 year ago
  • PAULA KESKINEN
    What are the environmental factors affecting growth in microorganisms?
    1 year ago
  • vappu
    How does environmental factors affect bacterial growth?
    1 year ago
  • marina diederich
    What are the environmental factors that influence microbia life?
    1 year ago
  • Karita
    What are the environmental factor that influence the growth of microorganisms?
    1 year ago
  • ethan martin
    What are the major enviromental condition that influence the growth of microorganisms?
    1 year ago
  • Junior
    Is organic matter an environmental factor that affects growth of microorganisms in soil?
    1 year ago
  • angela
    What are the effects of environmental factors on the growth of microorganisms.?
    1 year ago
  • Semrawit
    What influences bacterial growth?
    9 months ago

Post a comment