Chapter 6: Microbial Nutrition and Growth (Effect of oxygen down to binary fission)

Are use of oxygen and tolerance of oxygen the same thing?

No. The active use of oxygen and tolerance of oxygen are not the same thing

• Tolerance is the bacteria not being killed by oxygen

What are aerobes? What is an obligate aerobe and do they tolerate oxygen and can they use it in large quantities?

• Aerobes: use gaseous oxygen in their metabolism

• Obligate aerobe: An organism that cannot grow without oxygen with no exceptions (They tolerate oxygen and can use large quantities of requires oxygen ~20%)

What are microaerophiles? Do they require oxygen if so in what size of quantity?

Microaerophiles: are harmed by normal atmospheric concentrations of oxygen (~20%) (air around us) but require a small amount of it in metabolism

• Need oxygen but in smaller quantities less than ~20%

What are Facultative anaerobes? Do they grow in the presence or absence of oxygen and which is better? Can they tolerate large quantities?

Facultative Anaerobes: do not require oxygen for metabolism but use it when it is present

• Can grow in presence or absence of oxygen but better with oxygen

• They can tolerate large quantities (~20%)

What are Aerotolerant anaerobes? Are they harmed by oxygen and what do they use to break it down? Can they tolerate oxygen?

Aerotolerant Anaerobes: do not utilize oxygen but can survive and grow in its presence

• Not harmed by oxygen, mainly because they possess alternate mechanisms for breaking down peroxides and superoxide

• They can tolerate oxygen

Wha are Anaerobes? What are obligate anaerobes and do they tolerate/use oxygen? What will happen if exposed to it?

Anaerobes: lack the metabolic enzyme systems for using oxygen in respiration

• Obligate anaerobes lack the enzymes for processing toxic oxygen and die in its presence (Never use oxygen and don’t tolerate it)

• Obligate anaerobes will die if exposed to it

Wha does obligate mean?

Strict

What happens to oxygen when it enters cellular reactions? Are these intentional byproducts? Does this occur in human and bacterial cells?

It is transformed into several toxic products

• These are not intentional byproducts

• It does occur in human and bacterial cells

What are the several toxic byproducts created by oxygen? Do most cells have enzymes to neutralize these byproducts?

• Singlet oxygen (O), Superoxide ion (O2–), Hydrogen peroxide (H2O2), Hydroxyl radical (OH–)

• Most cells have developed enzymes that neutralize reactive oxygen by-products

What are the two enzymes that neutralize oxygen by-products? Are they needed together to neutralize? If so why?

• Two-step process requires two enzymes: Step 1. Superoxide dismutase and Step 2. catalase

• Both are required because step 1 creates hydrogen peroxide which is toxic

Describe the two step process of enzymes that break down oxygen byproducts. Do obligate anaerobes lack these enzymes?

Describe.

• Yes obligate anaerobes lack these enzymes

What are canophiles? Do they require CO2 and are they cultured in lots of CO2?

Canophiles: organisms that grow best at a higher CO2 tension than is normally present in the atmosphere

• They do require CO2 and are cultured in lots of CO2

What are the organisms that are important when isolating using lots of CO2?

• Important in the initial isolation of the following organisms from clinical specimens:

• Neisseria (a genus causing gonorrhea and meningitis)

• Brucella (undulant fever)

• Streptococcus pneumoniae

What’re the 3 types of microbe categories when talking about microbe growth when dealing with pH?

1. Neutrophiles

2. Acidophiles

3. Alkalinophiles

What are Neutrophiles? Is the ideal pH a value or range? What is the type of most of the microbes in the human body when talking about pH?

The majority of organisms live or grow in habitats between pH 6 and 8 (it’s a range around the neutral zone)

• Most microbes in humans are neutrophiles

What are acidophiles? What are alkalinophiles? Can some bacteria neutralize or alter pH?

• Acidophiles: organisms that thrive in acidic environments (pH less than 6)

• Alkalinophiles: organisms that thrive in alkaline conditions (pH more than 8)

• Some bacteria can alter or neutralize pH

What is the difference between osmotic pressure and atmospheric pressure?

Osmotic pressure: how much water is available for cells to use (from the surroundings)

Atmospheric pressure: air pressure (what we feel from our surroundings)

What are Osmophiles? What are Halophiles? Are they based on salt or sugar or both? What are the two types of Halophiles?

• Osmophiles: live in habitats with high solute concentration (salt or sugar)

• Halophiles: prefer high concentration of salt (only salt)

• There are obligate halophiles or facultative halophiles

Wha are Obligate halophiles? and provide an example of where they could live. Can we find this environment in the human body? Does salt have to be in the growth medium?

Obligate halophiles: Halobacterium and Halococcus grow optimally at solutions of 25% NaCl but require at least 9% NaCl. Ex: Salt lakes

• This is not an environment in the human body

• There must be salt in the growth medium

What are facultative halophiles And do they reside in high salt environments? Do they tolerate salt and can they grow without it? Do they grow the same with/without salt?

Facultative halophiles: remarkably resistant to salt, even though they do not normally reside in high salt environments. (Tolerate salt but can grow without high salt) Staphylococcus aureus can grow on NaCl media ranging from 0.1% to 20%

• They grow the same with or without salt

Do photographs use visible light as energy? Are they damaged by sunlight? Why do non photosynthetic microbes tend to be damaged by sunlight and can it kill them?

• Phototrophs use visible light rays as an energy source and are not damaged by the sun

• Nonphotosynthetic microbes tend to be damaged by the toxic oxygen products produced by contact with light (it can kill them)

What do some microbial species produce to absorb and dismantle toxic oxygen? Can different radiations be absorbed by different pigments?

Some microbial species produce yellow carotenoid pigments to absorb and dismantle toxic oxygen

• Different radiations can be absorbed by different pigments

How does Ultraviolet and ionizing radiation affect microbial cells and what are they used in? What specifically does it damage?

Ultraviolet and ionizing radiation can damage microbial cells and are used in microbial control

• Specifically damages microbial DNA but doesn’t kill endoscopes

Effect on atmospheric pressure: What are Barophiles? Under what range of pressure can they exist at? When do they rupture?

• Deep sea microbes

• Exist under pressures that range from a few times to over 1,000 times the pressure of the atmosphere

• These bacteria are so strictly adapted to high pressures that they will rupture when exposed to normal atmospheric pressure

What are the two main categories of associations between organisms? Does symbiotic affect one or both members? Does no symbiotic have to live in close association?

Symbiotic: organisms live in close nutritional relationships; required by one or both members (can impact one or both members)

Nonsymbiotic: Organisms are free-living; relationships not required for survival (Doesn’t have to live in close association)

What are the subcategories of symbiotic associations between organisms?

Mutualism: Both members benefit

Commensalism: One partner benefits; other member not

Parasitism: Parasite is dependent and benefits; host is harmed

What are the subcategories of nonsymbiotic associations between organisms?

Synergism: Members cooperate and share nutrients

Antagonism: Some members are inhibited or destroyed by others

What biofilms? What is the thin gel like fin on top of the community?

Mixed communities (Fungi, viruses, phages, etc.) of bacteria and other microbes that are attached to a surface and each other

• The thin gel like film on the top of the community protects it and is 3D

Explain the formation of a biofilm. What is a realize example of where biofilms can form?

• A “pioneer” colonizer initially attaches to a surface (the first microbe attaches)

• Other microbes then attach to those bacteria or a polymeric sugar or protein substance secreted by the microbial colonizers

• Can form on implanted medical devices

What is Quorum sensing? When it reaches a certain size what can happen?

Attached cells are stimulated to release chemicals as the cell population grows: to monitor the size of the population

• When it reaches a certain size the bacteria can stop growing and the bacteria can leave and go somewhere else