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Classification and Cell Structure

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Classifications and Species Characteristics



This section discusses Leuconostoc mesenteroides’ scientific classification and its basic background characteristics.  Leuconostoc mesenteroides’ classification as a lactic acid bacteria will be discussed in the section entitled "Lactic Acid Bacteria."



Scientific Classification and Cell Characteristics


Scientific classification is a means by which scientists group organisms with common characteristics.  Leuconostoc meseneroides’ scientific classification is below (the classification becomes more specific going from “Kingdom” to “Species.”)


  • Leuconostoc meseneroides is a species, and can be divided further into subspecies. 


  • Subspecies for example include Leuconostoc meseneroides subsp. meseneroides and Leuconostoc meseneroides subsp. cremoris.


  • Each subspecies has its own characteristics.









Scientific Classification of Leuconostoc meseneroides






























Leuconostoc mesenteroides





Classified in the Kingdom Bacteria, Leuconostoc mesenteroides share some characteristics with all bacteria: 





  • They have no nucleus surrounded by membranes.
  • They have no organelles surrounded by membranes.
  • They have a DNA strand.
  • They have a cell wall. 



In addition to the basic characteristics they share with others as members of the Bacteria Kingdom, Leuconostoc mesenteroides show the following characteristics. 









 All bacteria do not have the same shape. Typical shapes are cocci, rods, and spirals.  When Leuconostoc mesenteroides develop on solids, they are shaped as rods.  In liquids, Leuconostoc mesenteroides are shaped as cocci.  These cocci can be by themselves, with a few others, or joined together in long chains as shown below. 
















Source:  JGI Genome Analysis and System Modeling Group of the Life Sciences Division of Oak Ridge National Laboratory.

"Leuconostoc mesenteroides ATCC 8293." JGI Microbes . 7 Dec. 2008 <http://http://genome.jgi-psf.org/ finished_microbes/leume/leume.home.html>.


Photo: Fred Breidt, North Carolina State University



 Cell Wall

Gram Positive and Negative Bacteria






Source: "Gram stain: bacteria isolated and coloured with Gram stain." Online Photograph. Encyclopædia Britannica Online School Edition. 13 Dec document.write(new Date().getFullYear()); 2008  <http://school.eb.com/eb/art-709>.






Leuconostoc mesenteroides are Gram positive.  This means that they have an outer cell wall made of peptidoglycan.  To determine if a cell is gram positive or negative, the bacteria is stained with a crystal violet dye.  A purple color indicates peptidoglycan.  Peptidoglycan is a material made of a combination of sugars and amino acids.  The following is more detailed information the topic of Gram Staining.



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Gram Staining Video


     A gram stain is a technique invented in 1882 by a man named Hans Christian Gram to determine a certain classification of bacteria. A gram-positive bacteria has more peptidoglycan, less lipids, and a thicker cell wall than a gram-negative bacteria. The process of gram staining is adding a crystal violet stain to the cell, staining it that color. Then an iodine is added to the stain, so that it cannot be removed easily. You then use a decolorizer on it, which is a mixed solvent of ethonal and acetone. If the cell is gram-negative, the decolorizer will dissolve the lipid layer, allowing the violet iodine to diffuse into the solvent, causing the cell to not be a concentrated violet color, but more of a redish color. When the Decolorizer is added to a gram-positive cell, it dehydrates the cell, closing the pores and not allowing the stain to go anywhere. This leaves the cell wall as the crystal violet color. Lastly, a counterstain of fuchsin is added to the decolorized gram-negative cells, giving them a pink color. The bacteria Leuconostoc Mesenteroides happens to be a gram-positive bacteria, so if you performed Gram's staining method on it's cell wall and looked at it under a microscope, you would see that it has been stained violet.




                                                                                    Hans Christian Gram














Diagram of a Typical Gram + Bacteria such as Leucnosotoc Mesenteroides





Source: Bacteria: More on Morphology, http://www.ucmp.berkeley.edu/bacteria/bacteriamm.html


Plasma Membrane: This allows the transfer of material in and out of the cell.


Plasmid: These are loops of DNA, capable of being transmitted to other cells. They can also code proteins to make antibiotics inactive.


DNA: DNA is not surrounded by a membrane.


Ribosome: They produce proteins, although they are smaller than the eukaryotic cells of plants and animals.





Facultative Anaerobe


Another way in which bacteria are grouped is based on how they are affected by gaseous oxygen.  Aerobic bacteria require oxygen to live, grow and reproduce.  Anaerobic bacteria are just the opposite.  Leuconostoc mesenteroides is a facultative anaerobe.  Facultative anaerobes can grow whether or not oxygen is present.




Bacteria are either autotrophs or heterotrophs.  Autotrophs manufacture their own food by fixing carbon dioxide.  Their energy source is either from light or from oxidation of elements such as nitrogen.  Heterotrophs are opposite to autotrophs.  Heterotrophs do not make their own food.    Leuconostoc mesenteroides are heterotrophs.  They break down compounds from the environment for energy. 





 Leuconostoc mesenteroides is not a motile species.  Some bacteria do have flagella that help them to move, and an example is shown below.




Source: "Proteus vulgaris." Online Photograph. Encyclopædia Britannica Online School Edition. 13 Dec.  2008  <http://school.eb.com/eb/art-5490>.


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