Bacteria spore walls

The effectiveness of a disinfectant also depends upon the age of the microorganism. For example, young bacteria can easily be killed, while old bacteria are resistant. As the bacterium ages, a polysaccharide sheath is developed around the cell wall this contributes to the resistance against disinfectants. For example, when using 2.0 mg/L of applied chlorine dosage, for bacterial cultures of about 10 days old, it takes 30 min of contact time to produce the same reduction as for young cultures of about one day old dosed with one minute of contact time. In the extreme case are the bacterial spores they are, indeed, very resistant and many of the chemical disinfectants normally nsed have little or no effect on them. 

We can now see that the laying down of hard structures is a consequence of the radius-ratio eflFect as much as is the binding of calcium to the outer saccharides and proteins of cells. The walls of bacteria and spores have been extended by evolution to the celluloses of plants and bones and shells of animals. 

Occurrence The meso-form and occasionally its chiral isomers occur in the peptidoglycans of algal and bacterial cell walls. The meso-form is, in peptide-bound form, also a component of bacterial spores. The content amounts to 0.02 to 2.0% of the dry weight of the bacteria. D. is widely distributed. 

Clostridia have a Gram-positive cell wall that makes them different from other anaerobic, spore-forming bacteria. Figure 4.26 shows an example of Clostridia. 

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