Bohomolets Microbiology Lecture #3
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Transcript of Bohomolets Microbiology Lecture #3
Growth, development and cultivation of microbes
Evolution and classification of microorganisms
Possible mechanisms of propagation and surviving of procaryotic organisms
Mechanism Organisms
Fragmentation Actinomycetes, mycobacterium, mycoplasmas
Formation of spores Bacillus, Streptomycetes
Budding Mycoplasmas
Intracellular and extracellular forms formation
Chlamidiae
Formation of cyst Spirochetes
Change into nonculturable forms
Nonsporoforming parasite bacteria
Formation of L-forms Different bacteria
Inclusions of Chamidiae in infected cells
Growth
is a steady increase in all of the chemical components of an bacterium and usually results in an increase in the size of a cell
Steps of binary fission
a/ A parent cell prepares for division
b/ Enlarging of bacterium cell wall, cell membrane, and overall volume. The wall form the transverse septum, and the duplicated chromosome becomes affixed to a special membrane site.
c/ The wall septum grows inward, and the chromosomes are pulled toward opposite cell ends as the membrane enlarges.
d/ The septum is synthesized completely through the cell center.
Division of bacterial cell
Streptococcus pyogenes
Participation of mesosome in bacterium fission
N – nucleoid PC – cell wall MC – cytoplasmic
membrane M – mesosome S – septum
Doubling time of various bacteria under optimal conditions
Species Generation time (min)
Time required for one cell to grow to visible colony (hr)
Clostridium perfringens 10 8
Escherichia coli 20 16
Bacillus subtilis 28 23
Staphylococcus aureus 28 23
Mycobacterium tuberculosis 800 (>13 hours) 336 (2 weeks)
Treponema pallidum 1980 ( 33 hours) in rabbit testes
The phase of bacterial growth in closed system
1. The lag phase, during which vigorous metabolic activity occurs but cells do not divide.
2. The log (logarithmic) phase is when rapid cell division occurs.
3. The stationary phase in which the total number of viable cells remains constant.
4. The death phase in which the total number of viable bacteria decreases exponentially.
Continuous culture growing in chemostat
Multiplying bacteria
Reservoir with medium
Closed system – batch culture
Open system – continuous culture
Categories of media classification for bacteria cultivation
Consistency
Liquid
Semisolid
Solid
Bacteria growth in semisolid media
Categories of media classification for bacteria cultivation
Functional type
General purpose
Enriched
Selective
Differential
Specimen transport
Anaerobic growth
Enriched medium
Blood agar with Enterococcus faecalis
Differential media
MacConkey agar differentiates between lactose-fermenting bacteria (indicated by a pink-red reaction in the center of the colony) and lactose-negative bacteria (indicated by an off-white colony with no dye reaction).
Growth of bacteria with different requirements in oxygen in shake tubes
General methods of cultivation of anaerobe microorganisms
Anaerobe jars
Special medium for anaerobic growth
Methods of identifying bacteria
1. Microscopic analysis: shape, cell arrangement, inclusions, endospores, capsules, motility, Gram staining.
2. Culturing: appearance of colonies, including texture, size, shape, pigment; speed of growth and patterns of growth in liquid medium
3. Biochemical tests: detection products of microbial metabolism. Examples include tests for fermentation of sugars, capacity to digest proteins, presence of enzymes such as catalase, oxidase.
4. Molecular biological techniques: analysis of DNA sequences with DNA technology
5. Serological techniques: analysis of antigen properties.
Colonies of bacteria
Clostridium sporogenes
Bacillus spp.
Pseudomonas aeruginosa
Bacillus anthracis
Mycobacterium tuberculosis Mycoplasma pneumoniae
Colonies of fungi genus Microsporum
S - and R – forms of colonies
Bacterial pigments
Nocardia
Method for isolating bacteria
A pure culture is a population of microorganisms which are belonged to one species and grown on nutrient medium
Special terms
Strain is a culture of microorganisms derived from a single parent (organism or place).
Type is a culture of microorganisms which differs in structure or metabolism from other culture of that species.
Clone is a population of microorganisms that are descendents of a single mother cell
Subspecies in bacteria
♦ Subspecies
♦ Types: Morphovar (differs in structure of cell)
Chemovar (differs in metabolism)
Biovar (differs in number of biological features)
Phagevar (differs in susceptibility to bacterial viruses)
Serovar (differs in antigenic makeup)
Taxonomic ranks of the bacterium Leptospira interrogans
Formal rank Example Kingdom Prokaryotae
Division (Phymlum) Gracilicutes
Class Scotobacteria
Order Spirochaetales
Family Leptospiraceae
Genus Leptospira
Species interrogans
Taxonomy system of classification
Properties
A lot of different phenetic features
Chemical features
Antigenic features
Genetic features
Numerical taxonomy
Genetictaxonomy
Cheme-taxonomy
Serological taxonomy
Bergey’s Manual of Systematic Bacteriology. First edition – 1923.
Classification of bacteria based on one or number of the most characteristic features
Genera Species
Author’s name
Bacterial morphology
Disease’s name
Pigment forming
Habitat
Author’s name
Escherichia,Salmonella,Shigella
Vibrio, Staphylococcus, Streptococcus
Vibrio cholerae, Salmonella enteritidis
Staphylococcus aureus, Pseudomonas aeruginosa
Escherichia coli, Staphylococcus epidermidis
Shigella sonney, Borrelia burgdorferi