Study Guide Quiz #3
Control of Microorganisms:.
1. Why must we be careful in the choice of techniques to control microorganisms for
living vs. non-living matrices?
Some methods may prove to be harmful to living matrices like our bodies.
2. Describe several techniques that could be used to physically sterilize a table.
Bleach, Lysol, other harsh chemicals.
3. If you had a delicate instrument that you needed to sterilize, but it could not be heated
or subjected to harsh chemicals, what could you do?
UV radiation
Filtration is a great way of quickly sterilizing solutions without heating. Filters, of
course, work by passing the solution through a filter with a pore diameter that is too small for
microbes to pass through. Most filters are used today are membrane filters made from cellulose
esters. For removal of bacteria, filters with an average pore diameter of 0.2um is normally used.
But remember, viruses and phage can pass through these filters so filtration is not a good option
if these are a concern.
4.Be familiar with the modes of action of disinfectants/antiseptics in the following
categories: heavy metals, halogens, detergents, phenols, and strong oxidants.
Metals cause antiseptic action, because they easily combine with sulfhydryl-(SH) group
of thiolic enzymes, thus stopping the oxidizing process of microorganisms. When metal-ions
interact with human proteins, physical properties of the protein are usually altered; the protein
may be denatured and precipitation usually occurs. When the concentration of metal is low,
precipitation prevents deep tissue penetration and astringent action occurs. When the
concentration of metal is high, membrane and intracellular structures are damaged and caustic
or escharotic action occurs.
Halogens (chlorinated lime, chloramine B, chlorhexidine, iodinole, iodovidone). Antigerm activity of halogens depends on their ability to release chlorine and iodine. They form
chloric and iodic acids in water solutions. The latter release atomic oxygen and haloids. These
ions denature proteins of germs and act bactericidically. Chlorine is a strong oxidizing agent
and universal disinfectant.
Oxidizing agents are free atomic oxygen releasers. Atomic oxygen lead to irreversible
damage of oxidizing-restoring reaction of germ. The hydrogen peroxide has high killing
activity and a broad spectrum against bacteria, spores, viruses, and fungi when used in
appropriate concentration. It has the advantage that its decomposition products are not toxic
and does not injure the environment. Hydrogen peroxide is powerful oxidizer that is used
primarily as antiseptic.
Phenol itself perhaps the oldest of the surgical desinfectant/antiseptic. It is used to
disinfect urine, feces, and pus, for drug conservation. Phenol no longer used as an antiseptic
because of its corrosive effect on tissues, its toxicity upon absorption, and its carcinogenic
effect. When swallowed (with suicidal purpose) it causes buccal, esophageal and stomach
burns, excitation, convulsions, respiratory paralysis and vascular collapse.
Detergents or surface-active compounds decrease surface tension of cell membrane act, thus
alter it permeability. There are two kinds of detergents. They are cationic detergents
(quaternary ammonium compounds) and anionic detergents (soaps). The quaternary ammonium
compounds ("quats") are bacteriostatic, fungistatic, and sporistatic. They highly effective
against gram-positive bacteria and moderately active against gram-negative bacteria.
Strains of Mycobacterium tuberculosis and Pseudomonas aeruginosa are often resistant and
they are not effective against spore-forming organisms.
5. Why are chemotherapeutic agents, such as antibiotics, like the "magic bullet" that Paul
Ehrlich dreamed of back at the turn of the last century (hint: think of the reason for using
the antibiotic and the affect it has on the host cell).
This is because antibiotics tend to attack specifically the bad(transient) cells while bringing no
harm to the good(resident) cells. For example, Penicillin targets bad gram + cells.
Chemotherapeutic agents are used for germs killing inside the organism. Disinfectants and
antiseptics differ from chemotherapeutic agents by their low parasite selectivity and high
toxicity for systemic use.
6.Describe both broad-spectrum and narrow-spectrum antibiotics.
The term broad-spectrum antibiotic refers to an antibiotic that acts against a wide range of
disease-causing bacteria. A broad-spectrum antibiotic acts against both Gram-positive and
Gram-negative bacteria, in contrast to a narrow-spectrum antibiotic, which is effective against
specific families of bacteria.
7.How does penicillin work?
It interferes with the synthesis of peptidoglycan. This weakens the cell walls of dividing
bacteria, so they burst and die because of osmotic pressure (could become hypotonic or
hypertonic). This generally only occurs in gram+ cells.
6.Is penicillin equally effective for Gram + and Gram - cells?
No. Penicillin only targets Gram “+” cells effectively.
7. What about the synthetic penicillins?
The Synthetic penicillin have been altered in their groups attached to the beta lactam ring (NOT
the beta lactam ring) so that they may better affect the Gram - cells which aren’t as affected by
the natural b and v penicillins due to their thin Peptidoglycan layer that is harder to reach since
it is much thinner and protected by more layers than that of the gram + bacteria cells. They
have an extended range against some gram negative species.
8.What makes a microbe resistant to the action of penicillin?
The presence of the Penicillinase enzyme, usually within a plasmid contained by the bacterium,
targets and breaks the Beta-Lactam ring in the Penicillin
9. Why must care be taken when trying to control microbes in a living matrix?
Because you don’t want to accidentally bring harm to the good cells within a person’s body
10.Describe broad-spectrum and narrow-spectrum antibiotics.
The term broad-spectrum antibiotic refers to an antibiotic that acts against a wide range of
disease-causing bacteria. A broad-spectrum antibiotic acts against both Gram-positive and
Gram-negative bacteria, in contrast to a narrow-spectrum antibiotic, which is effective against
specific families of bacteria.
11. Why are chemotherapeutic agents, such as antibiotics, like the "magic bullet" that
Paul Ehrlich dreamed of back at the turn of the century (hint: think of the reason for
using the antibiotic and the affect it has on the host cell).
This is because antibiotics tend to attack specifically the bad(transient) cells while bringing no
harm to the good(resident) cells. For example, Penicillin targets bad gram + cells.
Chemotherapeutic agents are used for germs killing inside the organism. Disinfectants and
antiseptics differ from chemotherapeutic agents by their low parasite selectivity and high
toxicity for systemic use.
12. Why should you be concerned about the method you select to control some pathogenic
microbe in the bloodstream of a human?
Because the good cells may be at risk which could lead to problematic results, possibly even
fatal
13. Know the differences between disinfectants and antiseptics.
- Disinfectants=used IN non-living matrix
-
Antiseptics=used ON the living matrix
-
Disinfectants are used for non-living matrices and antiseptics are used for living
matrices. Disinfectants tend to be more harsh whereas antiseptics are more
friendly to cells such as human and animal cells.
14.Why can you sometimes use the same chemical as both a disinfectant and an
antiseptic?
You can use a disinfectant as an antiseptic in a situation where the good cells that the
disinfectant kill are not present, thus allowing it to function as an antiseptic.
15.What is the chief difference between broad and narrow spectrum antibiotics?
The term broad-spectrum antibiotic refers to an antibiotic that acts against a wide range of
disease-causing bacteria. A broad-spectrum antibiotic acts against both Gram-positive and
Gram-negative bacteria, in contrast to a narrow-spectrum antibiotic, which is effective against
specific families of bacteria.
16.What is the relationship between feeding animals food + antibiotics and the need to
discover new antibiotics?
When you feed animals you also have to give them antibiotics. However, these antibiotics will
give the bacteria an immunity to said antibiotics over time. As we eat the animals, we still get
over saturated with said antibiotics. Eventually we start to create a superbug, unless we can find
new antibiotics to keep the superbug from coming.
17. Understand the basic mechanism of bacterial resistance to penicillin.
Simply that bacteria may use the enzyme Penicillinase (usually found in their plasmids) to
break the Beta-Lactam ring??
Environmental Microbiology (Microbial Ecology):
1. How did the field Microbial Ecology develop and expand?
Tollund man was discovered and brought forth many studies with the questions. They
discovered how certain environments could exist to perfectly preserve a body if an
environment was anoxygenic, acidic, and had low temperatures. Microbial Ecology
developed as part of the Global Environmental Movement in the early 1970’s.
2. What types of things do microbial ecologists do?
Tollund man was discovered and brought forth many studies with the questions. They
discovered how certain environments could exist to perfectly preserve a body if an
environment was anoxygenic, acidic, and had low temperatures. Microbial Ecology
developed as part of the Global Environmental Movement in the early 1970’s.
3. What role(s) do microorganisms play in the functioning of ecosystems (think about
trophic diagrams)?
They can help to decompose as well as produce nutrients for others in their waste.
4. Where do nutrients associated with decomposition go when decomposers have
processed them?
They get released as waste back into the environment in forms such as O2 from H2O or S4
from H2S.
5. What storage sites in the environment act as reservoirs for nutrients that the
producers can use?
Soil, Bog, swamp, any location that can be isolated from oxygen usually absorbing the
chemicals without them being stripped away.