MCB 229 Spring 2000 Study Guide 4 Prof.
Terry
Covers Lecture for Feb. 10
This study guide is intended for you to use while you are
doing the assigned text reading. Quiz questions will be made with reference to
topics in this study guide. Quiz #4, based on questions from this study guide,
must be completed by midnight before the class on Thursday, Feb. 10. You will
need to create your "myWebCT" account and visit the MCB 229 WebCT page in order
to access this quiz.
Chapter 5
There’s a lot of terminology regarding nutrition, with
many terms ending in –troph (feeding). These terms are IMPORTANT!
The are widely used in scientific literature, and people don’t bother to
define them. Learn them well.
- It is convenient to classify elements into 3 categories: macronutrients (6
elements), micronutrients (4 elements) and trace elements (the other required
elements). Which elements belong to these 3 categories?
- The terms
autotroph and hetetotroph refer to C-source. What is the C-source
for each?
- The terms prototroph and auxotroph refer to
synthetic abilities for specific nutrients. How do they differ?
- The terms
phototroph, chemotroph, lithotroph, and organotroph
refer to energy source (sometimes the same as C-source, but often different). To
what do these terms refer? These terms will seem useless at first, but just
wait. As we learn more about specific microbes, they will become
indispensable.
- In practice, microbes are defined in terms of both their
C-source and their Energy source together; thus terms such as
“Chemolithotophic autotroph”, “Photoorganotrophic
heterotroph”, “Photolithotophic autotroph”,
“Chemoorganotrophic heterotroph” are common. For each such
description, be able to identify how the organism obtains its C and its
energy.
- But wait, it gets even more confusing! Some organisms are
mixotrophs! What is their claim to fame?
- We’ll come back later
to how organisms acquire S, P, and N. skim this section on p. 100.
- Skim the
section on growth factors and vitamins (pp. 100-101)
- What is the difference
between passive diffusion, facilitated diffusion, and active
transport? Note that, although facilitated diffusion is common inside the
animal body, it is not common in procaryotes. Considering that bacteria are
unicellular and have little control of their environment, suggest a reason why
active transport mechanisms are preferred.
- When “active
transport” is mentioned, most biology students think only of ATP-pumps in
which transport is linked to ATP hydrolysis. Many bacteria use ion gradients to
power active transport with a number of carriers. Ion gradients can be coupled
either in symport or antiport fashion. What is the difference?
- Yet another way of powering active transport is group translocation.
Instead of ATP or ion gradients, a different molecule with high-energy phosphate
provides initial activation energy that is ultimately coupled to entry of
substrate with accompanying phosphorylation. The PTS system in E. coli is
a common example, though by no means an isolated one. Examine Fig. 5.4 and note
the stages of PTS. Be able to recognize and distinguish this type of transport
from those mentioned above.
- Iron poses a special problem. Iron occurs in two
ionic forms: Fe++ (ferrous iron) and Fe+++ (ferric iron).
At pH 7, Fe+++ reacts with water to form an insoluble precipitate,
Fe(OH)3, more commonly known as “rust”. This removes iron
from availability, so what is a poor microbe to do? The answer is
“siderophores” – what are they? Look at Fig. 5.5 and be able
to recognize typical siderophores by name.
- The remainder of Ch. 5 discusses
culture media, a topic also explored in lab. This is important practical
information in order to appreciate why different media are used for different
purposes. Be familiar with the following terms: defined medium,
complex medium, agar, selective medium, differential
medium.
- The discussion of pure culture isolation on
streak plates and pour plates should be familiar from your lab experience. Skim
this section (pp. 107-111)
.
Ch. 6. Microbial Growth
- Examine Fig. 6.1 and note the location of lag, log, stationary, and death
phase. What factors determine which phase occurs?
- For now, skip the
"mathematics of growth" (pp. 115-116). We’ll cover relevant details in
class.
- What is generation time? In Table 6.2, what organism has the fastest
generation time? The slowest? Are procaryotes faster than eucaryotes?
- What
does a Petroff-Hauser counter do? How does the cell number reported by a P-H
counter differ from a viable count?
- What is a C.F.U., and how does it differ
from # of microbes/ml?
- Be able to calculate C.F.U. from assays of a
dilution series. For example, if you measure 25 colonies when plating 1 ml. of a
10-6 dilution, what is the C.F.U. of the undiluted mixture? How would
your answer change if you had sampled 0.5 ml of a 10-6 dilution and
found 25 colonies?
- What is the simplest and most sensitive technique for
measuring bacterial mass?
- Skim "Growth yields ..." on pp. 120-121.
- What
is the difference between batch and continuous culture
systems?
- How does a chemostat work (examine Fig. 6.11)? How does it
differ from a turbidostat?
- Skim "Balanced and unbalanced growth" on
pp. 112-123.
- The section "Influence of Environmental Factors on Growth" is
important and should be read with care. There are any terms that microbiologists
use regularly to describe an organism's environmental preferences. What do each
of the following mean? Extremophile, osmotolerant, halophile, acidophile,
neutrophile, alkalophile, stenothermal, eurythermal, psychrophile, psychrotroph,
facultative psychrophile, mesophile, thermophile, hyperthermophile, obligate
aerobe, obligate anaerobe, facultative anaerobe, aerotolerant anaerobe,
microaerophile, barotolerant, barophile?
- What is a compatible solute?
Give two examples of such solutes used by bacteria, and two different examples
of such solutes used by fungi.
- What is water activity? How is it related
humidity? Comparing bacteria and fungi as a group, which group can tolerate
lower aw environments? What metabolic trick do halophilic
bacteria use to survive in high salt environments?
- How do bacteria and fungi
differ in their optimal pH for growth, as a rule?
- What is the internal pH
of a bacterium that grows at pH 1?
- When E. coli is placed in an acidic
environment (below pH 5.5), does it adjust, and if so how?
- What do the
cardinal temperatures measure?
- What adaptations allow psychrophiles
to grow at temperature where other bacteria won't grow at all? What adaptations
allow thermophiles to grow at temperature where other bacteria won't grow at
all?
- What is it about oxygen that anaerobes can't stand? I.e., what specific
mechanisms differentiate aerobes from anaerobes? (Hint: think enzymes).
- What
types of damage does ionizing radiation produce in cells? What damage is caused
by UV light? Does ordinary visible light cause any problems for bacteria? How do
bacteria that are airborne, and thus often exposed to light, cope with potential
damage?