BACTERIOLOGY (STM 311) SECOND LECTURE

BACTERIOLOGY SECOND LECTURE

PROTOPLAST

          A protoplast is the cytoplasm of the bacterium plus the cellular inclusion. The protoplast is devoid of the cell wall i.e. bacterium without a cell wall, protoplast can be prepared by either treating the cell wall with a lysozyme that will destroy the cell wall or culturing the bacterium.

          In a medium sublimated with antibiotics. The environment of the protoplast must be highly osmotic must be isotonic to the bacterium, to prevent the bacterium from bursting, some bacteria are found in environment that are hypertonic. It would have expected that water will be drawn from the environment into the bacterium cell. This happens but as the bacteria continues to take in water and the protoplast swells, the cell wall prevent the protoplast from swelling beyond unit, and hence, it does not burst.

SHAREOPLAST

          Shareoplast formation is more synonymous with Gram negative bacteria than Gram positive bacteria. This is because they possess an outer membrane in addition to the cytoplasmic membrane; shaeroplast can be prepared in the same way as protoplast i.e by enzymatic hydrolysis of the cell wall or by growth in a nutrient medium sublimated with antibiotics (penicillin).

          A cell without the cell wall but having an outer membrane in addition to the cytoplasmic membrane is called the shaeroplast.

          Another organism that has the same type of structure with shareoplast is mycoplasmas. Mycoplasmas do not possess cell walls and most of them are parasitive in animals, plant and protozoa. On agar medium their culture gives the fried egg appearance, the mycoplasmas are made up only of cell membrane and they are only able to thrive on osmotically favorable environment i.e. Isotonic environment because they do not have a cell wall.

          Mycoplasma can either be facultative anaerobic organism that can grow in both presence and absence of oxygen or strict anaerobic organism that can grow only in the presence of oxygen.

          Mycoplasma colonies are very tiny and can hardly be seen on the solid medium except we use a low power microscope. Most colonies are submerged inside the medium.

          Mycoplasmas are very fragile but they increase strength of their membrane by channeling cholesterol in the structure of the membrane to increase its rigidity. Most mycoplasmas are spherical in shape except a genre in the order mycoplasmatales is called Spirolasma which is helical in structure. It is not understood how this member obtain a structure that is different from other plasmas.

INTRACYTOPLASMIC INCLUSION IN MICROBIAL SYSTEM

          Several microbes are known to possess special quality that enables them to perform special functions. Intracytoplasmic inclusion is common among the members of photoautotrophic organisms etc. in this organism; the cytoplasmic membrane is thrown into series of invagination to form mesosomes. Some of this invagination extend in the Centre of the organism and refer to as central mesosomes are believed to be use as primitive spindles for the division of DNA and cytoplasm during binary fission in bacteria.

          The peripheral mesosomes are used as electron transport surfaces during breakdown of substrates in bacteria and other photosynthetic group, the in folded cytoplasm increases the surface area at which either photosynthesis or respiratory processes can take place.

L – FORMS

          The L-forms of bacteria look like sphaeroplast but are different from them because they possess some part of wall materials, such forms of organism always result has a result of exposure of the normal organism to stress or sub lethal conditions.

          This treatment result in the destruction of the cell wall partially with the result that a protoplast carrying cell wall attached is formed. L-forms can revert to the normal organism if the stress condition is removed.

DIFFERENCES BETWEEN L-FORMS AND MYCOPLASMA

S/N	L-FORMS	MYCOPLASMA
1	They have cell wall	Lacks cell wall materials
2.	Can revert back to the normal bacteria when the stress conditions is removed	Cannot revert back to any other condition
3.	Penicillin bound protein and peptidoglycan precursors are present in the membrane of the walls of L-forms	Lacks penicillin bound protein and peptidoglycan precursors.
4.	Are derived from wall bacteria	Are not derived from wall bacteria
5.	Are produced from sub lethal treatment of wall bacteria	Are not produced from sub lethal treatment of wall bacteria.
6.	Colony of L forms are large on plate	Colonies of mycoplasma are minute on plate.

SIMILARITIES BETWEEN L-FORMS AND MYCOPLASMA

    1.      They both have fried egg appearance.     

    2.      They both osmotically stable.

CLASSIFICATION OF BACTERIA

          In biology as well as several other fields, classification portrays the orderly arrangement of units under study into groups of larger unit. The classification used today in biology came into being as a result of the work as a Swedish naturalist (botanist) called Carl Linnaeus (1707 – 1778) his work was published in 1935-, the book he wrote on classification has formed the basis for botanical and zoological Nomenclature. This is a system of many plant and animals. Nomenclature in Microbiology which came long after the work of Linnaeus was based on the principle he laid down for plant and animal kingdom, he use the binomial system of nomenclature.

          Earlier classification before Carl’s work had classified all living organisms into one of two kingdom; plant and animal. Remember that in microbiology we studied organism which are like plant and animal because they are organism which does not form naturally with plant or animal it became necessary to proposed new kingdom into which neither organism nor animals could be grouped. Furthermore to the above proposal Haeckel a German zoologist proposed a kingdom Protista should include unicellular organism that are neither plant nor animals, the organization include bacteria, algae, fungi and protozoa, (because virus are not cellular organization they are not classify as protist) bacteria are referred to as lower protest whereas Algae, Fungi and Protozoa are referred to as higher protist.

PROCARYOTICS AND EUCARYOTICS

        The Kingdom Protista exposed by Haeckel is sad with numerous flaws: look at this, how can we distinguish bacterium from yeast or some microscopic algae? What criteria can we use to separate these two organisms from one another? The convincing bacteria were not available then until recently (1940) when it became possible to observe the internal structure of some cells with the help of powerful magnification provided by the electron microscope. It was possible to observe in some cells like those of bacteria that the nuclear material was naked with the absence of a nuclear material was naked with the absence, of a nuclear envelope (membrane) on the other hand, cells of algae and fungi have their nuclear materials bound by the nuclear membrane.

          This observation of a nucleus which was not membrane bound in Algae, fungi and protozoa were an observation with basis significance. Further work has added more facts on the different of this group based in internal structures. Therefore the bacteria fall into the procaryotic organization and algae and fungi into the eucaryotic group, the organization accordingly it should be noted here that plant and animal are also eucaryotes.

DIFFERENCES BETWEEN EUCARYOTES AND PROCARYOTES

S/N		EUCARYOTES	PROCARYOTES
1.	Genetic organism – Nucleoplasm bounded with membrane	+VE	-VE
2.	No of chromosome	Greater than 1	1
3.	Chromosome contain histones	+VE	-VE
4.	Nuclear division by mitosis	+VE	-VE
5.	Presence of Nucleolus	+VE	-VE
6.	Presence of DNA in  organelles	+VE	-VE
7.	Means of genetic recombination
I.	Fusion of gametes	+VE	-VE
II.	Formation of partial diploids by unidirectional transfer of DNA	-VE	+VE

‘a’ – some genetic information non-essential for basic cellular function may be in separate genetic element (plasmids).

DIFFERENCES IN REFERENCE TO CYTOPLASMIC STRUCTURE

S/N		EUCARYOTES	PROCARYOTES
1.	Endoplasmic reticulum	+VE	-VE
2.	Golgi apparatus	+VE	-VE
3.	Lysozyme	+VE	-VE
4.	Mitochondria	+VE	-VE
5.	Chloroplast	+VE or -VE	-VE
6.	Ribosome 80s (Cytoplasmic)                 70s (Organelles)	80s (Cytoplasmic) 70s (Organelles)	70s (Ribosome)
7.	Micro tubular system	+VE	-VE
8.	Organelles bounded by a non-unit membrane	-VE	+VE
9.	Presence of cell wall containing peptidoglycan

SOME FUNDAMENTAL ATTRIBUTES FOUND EXCLUSIVELY IN EUCARYOTES

      1.      Phagocytosis.

      2.      Pinocytosis.

      3.      Secretion of materials in Golgi vesicles.

      4.      Intracellular digestion.

      5.      Maintenance of cellular endosymbionts.

      6.      Directed Cytoplasmic – steaming and Amoeboid movement.