Micro Slide 5 .. by salam ahmad

8/3/2019 Micro Slide 5 .. by salam ahmad

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Reproduction of organisms and their cells

y Prokaryotic cell reproduction

Prokaryotic cells reproduce by a process known as binary fission one cell

splits in half to become two daughter cells.

y Before a prokaryotic cell divides in half, the chromosome must be

duplicated.

The time it takes for binary fission to occur is called the generation time.

y G

eneration time varies from one species to another and depends on growthconditions (E, coli has a generation time of ~20 minutes).


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Taxonomy

y Taxonomy is the science of classification of living organisms.

y Taxonomy consists of classification, nomenclature and identification.

y Classification is the arrangement of organisms into taxonomic groups

(known as taxa).

y Tool for remembering the sequence ofTaxa.

- king David came over for Good Spaghetti

KDCOFGS, K for Kingdom, D for Division, C for Class, O for order, F for

Family, G for Genus and S for species.

Microbial Classification

y The science of taxonomy was established on the binomial system of

nomenclature.

y In the binomial system, each organism is given 2 names- Genus and the specific epithet Taken together, both names constitute

the species.

- For example, Escherichia coli; Escherichia is the genus and coli is the

specific epithet.

- The genus is frequently abbreviated with just a single letter, (e.g. , E for

Escherichia).

y The abbreviation sp. Is used to designate single species and spp. For

more than one species.


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Microbial Classification

y Organisms are categorized into larger groups based on their similarities and

difference.

y The five Kingdom system of classification

1- Bacteria and Achaeans Kingdom procaryotae

2- Algae and protozoa Kingdom protiste

3- Fungi Kingdom fungi

4- Plants Kingdom plantae

5- Animal Kingdom Animalia

y Viruses are not included because they are acellular.

y Other systems of classification do exist.

Microbial Classification (continued)

y The three-Domain system of Classification

1- Archaea (prokaryotic)

2- Bacteria (prokaryotic)

3- Eocarya (all eukaryotic organisms)

y The three-Domain system is based on differences in the structure of certain

Ribosomal RNA (rRNA) molecules among organisms in the 3 domains.


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Determining Relatedness Among Organisms

y The most widely used technique for gauging diversity or relatedness or

organisms is called ribosomal RNA (rRNA ) sequencing.

y Ribosomes are composed of two subunits; a small subunit.

y The small subunit is composed of only one rRNA molecule, which is coded

for by a gene called the 16S Rrna gene in prokaryotes and the 18S rRNA

gene in eukaryotes.

Determining Relatedness Among Organisms

(Continued)

To determine how closely related one procarytic organanism is to

another, scientists compare the sequence of nucleotide base pairs in the

16S eRNA gene from one of the paganisms to the sequence of base pairs in

the 16S rRNA gene from the other organisms.

y The more similar the sequences of base pairs, the more closely related are

the organisms.


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Chapter 4 Outline

y Categories of Microorganisms

y Aceliular Infectious Agents

- Viruses

- Virolds and prions

y

TheD

omainB

acteria

- Characteristics

- Unique Bacteria

- Photosysthemtic Bacteria

y The Domain Archact

Categories of Microorganisms

y Microbiology is the study of Microorganisms.

y Microorganisms can be divided into those that are truly

Cellular (bacteria, Achaeans, algae, protozoa and fungi)

And those that are a cellular (viruses, viroidsand prions).


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y Cellular microorganisms can be divided into those that are prokaryotic

(algae, protozoa and fungi).

y Viruses, virolds and prisons are often referred to as infectious agents or

infectious particles

A cellular Infectious agents (continued)

*Viruses

- Complete virus particles are called virus.

-Most viruses are from 10 to 300 nm in diameter .

-Viruses inflect humans animals, plants fungi , protozoa algae and bactenal cells

.

-Some viruses called acrogenic viruses or oncviruses ,cause speclnc types of

cancer .

-A typical virus consts of genome of either DNA or RNA surrounded by a cupid

(protein coat) which is composed or protein units called cashmeres.

Some virus (enveloped vertices) have an outer envelope composed of kpids and

polysaccharides.

A cellular Infectious agents (continued)

Viruses have 5 properties that distinguish them from living cells.

1- They possess either DNA or RNA living cells possess both.

2- They are unable to replicate on their own.


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3- Unlike cells, they do not divide by binary fission, mitosis or meiosis.

4- They lack, the genes and enzymes necessary for energy production.

5- They depend on the ribosomes, enzymes and metabolites of the host cell

for protein and nucleic acid production.

Acellular Infectlous agents (continued )

*viruses are classified by :

*Type genetic material( either DNA or RNA) .

*Shaps and size of capsid.

*Number of capsomeres .

*Presence or absence of an envelope.

*Type of host it infects.

*disease it produces .

* Target cell .

*Immunologic \antigenic properties .


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Micro Slide 5 .. by salam ahmad