Introduction to Bacteria
Session 3: Introduction to Bacteria
Total Session Time: 120 minutes
Pre-requisites
Students Learning Tasks
By the end of this session students are expected to be able to:
requirements and morphology
Resources Needed:
SESSION OVERVIEW
|Step |Time |Activity/ |Content |
| | |Method | |
|1 |5 minutes |Presentation |Introduction, Learning Tasks |
|2 |20 minutes |Presentation |Common Terminologies used in |
| | | |bacteriology |
|3 |30 minutes |Presentation |Bacterial Growth and Reproduction |
|4 |20 minutes |Presentation |Characteristics of Bacteria |
|5 |35 minutes |Presentation |Classification of Bacteria |
|6 |5 minutes |Presentation |Key Points |
| 7|5 minutes |Presentation |Evaluation |
SESSION CONTENTS
STEP 1: Presentation of Session Title and Learning Tasks (5 minutes)
READ or ASK students to read the learning tasks and clarify
ASK students if they have any questions before continuing
STEP 2: Common Terminologies Used in Bacteriology (20 minutes)
o Bacteriology is the study of bacteria
o Bacteria are prokaryotic organisms that replicate by binary
fission. Other prokaryotic organisms are the archaea
o A substance that inhibit replication or growth of bacteria
o A substance that kills the bacteria
o A blend of nutrients where microorganisms are made to grow in the
laboratory
o Is the process of applying dyes to a smear of microorganisms fixed
on slide in order to make certain structures visible
o Microbial flora harboured by normal, healthy individuals
o The ability of an infectious agent to cause disease
o A microorganism capable of causing disease
o An agent capable of causing disease only when the host’s immunity
is impaired
o Multiplication of an infectious agent within the body.
Multiplication of the bacteria that are part of the normal
microbiota of the gastrointestinal tract, skin, and so on is
generally not considered an infection
o The ability of a microorganism to produce a toxin that contributes
to the development of disease
o The quantitative ability of an agent to cause disease. Virulent
agents cause disease when introduced into the host in small
numbers. Virulence involves adherence, persistence, invasion, and
toxigenicity
o A person or animal with asymptomatic infection that can be
transmitted to another susceptible person or animal
STEP 3: Bacterial Growth and Reproduction (30 minutes)
increase in number via reproduction by binary fission
daughter cells and the two daughter cells produce four cells and so
forth.
generation time
liquid (e.g. broth)
the following phases of growth;
o Lag phase or adaptive phase
o Logarithmic phase or exponential phase
o Stationary phase
o Decline phase
o Environmental factors e.g. availability of water, nutrients, pH,
oxygen concentration and solute concentration
o Physicochemical factors e.g. temperature, pH, solute, availability
of oxygen etc.
plotted on growth rate Vs factor to clearly show impact of varying the
factor on growth rate
o Such plots/graphs include
nutrients formulated in growth media. These are available commercially
for growing different types of bacteria in the laboratory
o E.g. MacConkey agar (for Gram negative bacteria), Blood agar
(grows a variety of bacteria) etc.
the number of cells
STEP 4: Characteristics of Bacteria (20 minutes)
|Activity: Buzzing (5 minutes) |
| |
|ASK students to pair up and buzz on the following question for 2 |
|minutes |
| |
|What are the characteristics of bacteria? |
| |
|ALLOW few pairs to respond and let other pairs to add on points |
|not mentioned |
| |
|WRITE their response on the flip chart/board |
| |
|CLARIFY and SUMMARIZE by using the content below |
nucleus
STEP 5: Classification of Bacteria (35 minutes)
o Microscopic appearance of cells i.e. bacteria are classified
according to their shapes
o Cocci
in chains
bacteria in clusters
pairs
o Bacilli
include;
cocci
o Spirillum
o Vibrio
o Spirochete
o Staining properties with Gram stain
alcohol
washed with alcohol
o Biochemical reactions (based on ability to carry out biochemical
reactions as sugar fermentation (i.e. fermenters and non-
fermenters)
o Production of enzymes. For example;
breaks down hydrogen peroxide
negative
o Oxygen requirement
o Spore formation
o Intracellular or extracellular growth
o Fastidious/non fastidious bacteria
STEP 6: Key Points (5 minutes)
characteristics and morphology
STEP 7: Evaluation (5 minutes)
References
Hugo and Russell (2011), Pharmaceutical Microbiology 8th Edition, Willey-
Blackwel publications
Karen C. Carroll et al (2013); Jawetz, Melnick and Adelberg’s Medical
Microbiology 26th Ed. McGraw Hill Co. Inc.
Greenwood et al (2012); Medical Microbiology, 18th edition Churchill
Livingstone
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