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