MB 351 - Lecture 17

Question 1

Pure Culture

Answer 1

bacteria usually exist in mixed populations,
so it is important to obtain a pure culture to study the cultural, morphological, and physiological characteristics of an individual species
-pure culture is a population containing only one type of organism
-ideally derived from a single cell

Question 2

Mixed culture

Answer 2

populations of different organisms are present

Question 3

Technique used to obtain a single isolated strain for study

Answer 3

Aseptic pure culture techniques

Question 4

Colony

Answer 4

a visible mass of microbial cells arising from one cell or spore or from a group of the same microbes

Question 5

A colony is often called a

Answer 5

colony-forming unit (CFU)

Question 6

The ______ method is used to isolate pure cultures

Answer 6

streak plate (T-streak)

Question 7

Biofilms

Answer 7

biofilms usually consist of a mixed bacterial population. These communities consist of sessile organisms, meaning that they grow attached to a surface.

• share nutrients
• sheltered from harmful factors
• may be responsible for many chronic infections and diseases

1,000 times more resistant to antibiotics
70% of all microbial infections are caused by biofilms

Question 8

Biofilms structure consisting of…

Answer 8

microcolonies enclosed in a hydrated matrix of microbially produced: proteins, nucleic acids, and polysaccharides, often called SLIME or HYDROGEL
-resistant to environmental stresses and antibiotics

Question 9

Planktonic

Answer 9

floating or free-living cells

Question 10

Stages of developing biofilm

Answer 10

1. reversible attachment of bacterial cells to surface
2. irreversible attachment mediated by formation of polysaccharides, etc.
3. formation of microcolonies and the beginning of biofilm maturation
4. formation of a mature biofilm with a 3D structure containing cells packed in clusters with channels between the clusters that allow transport of water and nutrients and waste removal
5. detachment and dispersion of cells from the biofilm and initiation of new biofilm formation.

Question 11

Bacteria that become part of a biofilm engage in _________

Answer 11

quorum sensing “chemical vocabulary”

Question 12

BSL 1 - Biosafety Levels

Answer 12

microbes there are not known to
consistently cause disease in healthy adults and present minimal potential hazard to
laboratorians and the environment. An example of a microbe that is typically worked with at a
BSL-1 is a nonpathogenic strain of E. coli. Work can be done on an open lab bench, requires
a sink. Requires personal protective equipment (PPE) such as lab coats, gloves, eye
protection.

Question 13

BSL 2

Answer 13

If you work in a lab that is designated a BSL-2, the
microbes there pose moderate hazards to laboratorians and the environment. The microbes are
typically indigenous and associated with diseases of varying severity. An example of a
microbe that is typically worked with at a BSL-2 laboratory is Staphylococcus aureus. It
includes various bacteria and viruses that cause only mild disease to humans, or are difficult to contract via aerosols in a lab setting, such as Clostridium difficile, most Chlamydiae, hepatitis
A, B, and C, influenza A viruses, Salmonella. BSL-2 differs from BSL-1 in that: laboratory
personnel have specific training in handling pathogenic agents and are directed by scientists
with advanced training; access to the laboratory is limited when work is being conducted;
extreme precautions are taken with contaminated sharp items; and certain procedures in which
infectious aerosols or splashes may be created are conducted in biological safety cabinets or
other physical containment equipment.

Question 14

BSL 3

Answer 14

is required for work involving indigenous or exotic agents, and they can cause serious
or potentially lethal disease that are transmitted through the air (via aerosols). Respiratory
transmission is the inhalation route of exposure. Laboratory personnel must receive specific
training in handling pathogenic and potentially lethal agents, and must be supervised by
scientists competent in handling infectious agents and associated procedures. Lab personnel
are under medical surveillance and might receive immunizations for microbes they work with.
All procedures involving the manipulation of infectious materials must be conducted within
Biosafety Cabinets (BSCs) (shown at the top image), or other physical containment devices, or
by personnel wearing appropriate personal protective equipment (eg respirators). A BSL-3
laboratory has special engineering and design features that prevent the release of
microorganisms to the environment. Facilities have hands free sink, exhaust air cannot be
recirculated, entrance is through two sets of self closing and clocking doors. Microbes that are
worked on in BSL3 facilities are Mycobacterium tuberculosis which cause tuberculosis, etc.

Question 15

BSL 4

Answer 15

labs builds on the containment requirements of BSL-3 and is the highest level of
biological safety. BSL-4 labs is required for work with dangerous and exotic agents that pose
a high individual risk of life-threatening disease, aerosol transmission or unknown risk of
transmission. The microbes in BSL4 labs cause infections that are frequently fatal and
generally there are no vaccines or treatments for these infections. There are only a small
number of such labs in the U.S. All handling of agents must be performed in a gas tight Class III Biosafety Cabinet or by a personnel wearing a positive pressure protective suit. Work with Ebola.