Introduction to Bacteria – PST05103 Pharmaceutical Microbiology
NTA Level 5 • Semester 1 • PST05103 Introduction to Bacteria Pharmaceutical Microbiology • Source Session/Topic 3 Full source-text version: all educational wording from the extracted learning source is retained; only presenter/tutor metadata and web-layout noise are removed, while formatting is improved for readability. Session 3: Introduction to Bacteria Total Session Time: 120 minutes Pre-requisites • Human anatomy and physiology Students Learning Tasks By the end of this session students are expected to be able to: • Define terms used in bacteria • Describe bacterial occurrences and distributions • Classify bacterial according to staining properties, nutritional requirements and morphology Resources Needed: • Flip charts, marker pens, and masking tape • Black/white board and chalk/whiteboard markers 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) • Bacteriology o Bacteriology is the study of bacteria • Bacteria o Bacteria are prokaryotic organisms that replicate by binary fission. Other prokaryotic organisms are the archaea • Bacteriostatic o A substance that inhibit replication or growth of bacteria • Bactericidal o A substance that kills the bacteria • Growth medium o A blend of nutrients where microorganisms are made to grow in the laboratory • Staining o Is the process of applying dyes to a smear of microorganisms fixed on slide in order to make certain structures visible • Microbiota o Microbial flora harboured by normal, healthy individuals • Pathogenicity o The ability of an infectious agent to cause disease • Pathogen o A microorganism capable of causing disease • Opportunistic pathogen o An agent capable of causing disease only when the host’s immunity is impaired • Infection 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 • Toxigenicity o The ability of a microorganism to produce a toxin that contributes to the development of disease • Virulence 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 • Carrier 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) • In bacteria growth an increase in number of cells or biomass. They increase in number via reproduction by binary fission • Bacteria population grow in exponential fashion. One cell produces two daughter cells and the two daughter cells produce four cells and so forth. • The time interval between one cell division and the next is called generation time • Bacteria growth can occur on solid surfaces (e.g. on agar plate) or in liquid (e.g. broth) • Growth in bacteria can be in open or closed culture • Bacteria growth in closed culture (closed batch liquid culture) show the following phases of growth; o Lag phase or adaptive phase o Logarithmic phase or exponential phase o Stationary phase o Decline phase • Various factors affect bacterial growth • Factors that influence bacterial growth include; 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. • Optimum growth occurs at very conducive environment • Effect of various factors affecting growth e.g. temperature, can be plotted on growth rate Vs factor to clearly show impact of varying the factor on growth rate o Such plots/graphs include ▪ Growth Vs temperature ▪ Growth Vs pH ▪ Growth Vs oxygen concentration etc. • Bacteria growth requirement in the laboratory are achieved by using 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. • Bacterial growth can be measured by various methods e.g. by counting 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 | • They are prokaryotic i.e. they lack nuclear membrane so no true nucleus • Bacteria are unicellular • Cell wall is made up peptidoglycan • Bacteria reproduce by binary fission • DNA is circular • They do not have membrane-bound organelles • Metabolism in bacteria i.e. variety of pathways • Movement in bacteria i.e. flagella STEP 5: Classification of Bacteria (35 minutes) • Bacteria are classified according to different criteria • Morphology o Microscopic appearance of cells i.e. bacteria are classified according to their shapes o Cocci ▪ Bacteria that are spherical in shape. They include; • Streptococci (singular: Streptococcus) –Spherical bacteria in chains • Staphylococci (singular: Staphylococcus) –Spherical bacteria in clusters • Diplococci (singular: diplococcus) –Spherical bacteria in pairs o Bacilli ▪ Bacteria that are rod-shaped or cylindrical bacteria. They include; • Streptobacilli (in chains) • Coccobacilli –short round rods, oval and they look like cocci o Spirillum ▪ Bacteria are spiral in shape o Vibrio ▪ Bacteria are comma-shaped i.e. curved-rods o Spirochete