If lysozyme has the ability to attack the binding between NAG and NAM, it should be able to do that during all growth phases. But some bacteria (Gram-positive) become resistant to lysozyme in the stationary phase.
Could the reason be a modification of the peptidoglycan during the stationary phase, which make the bacteria resistant to lysozyme?
It is rather logic that growing bacteria are more susceptible, because during extension growth and also cell division the wall has to be rearranged, offering weak points for destruction. In addition, stationary phase cells generally run a survival programme, i.e. among others they prepare for harsh conditions (drying in particular). Thus, the structure of cell wall is reinforced and the water content decreased, polymers may be additionally masked by amorphous matter to cement the structure. Lysozyme has a rather large molecule, thus it may be a problem to simply deliver it into the entire cell wall structure to act on peptiglycan bonds.
It is easier to dismantle a wall while it is being built than to do the same after it is established high and dry - the same logic may hold an answer to your question, Mohammad.
It is rather logic that growing bacteria are more susceptible, because during extension growth and also cell division the wall has to be rearranged, offering weak points for destruction. In addition, stationary phase cells generally run a survival programme, i.e. among others they prepare for harsh conditions (drying in particular). Thus, the structure of cell wall is reinforced and the water content decreased, polymers may be additionally masked by amorphous matter to cement the structure. Lysozyme has a rather large molecule, thus it may be a problem to simply deliver it into the entire cell wall structure to act on peptiglycan bonds.
Thanks for the interesting discussion
Some Gram positive can be easily protoplasted by lysozyme in the stationary phase (such as Streptomyces) while others become resistant to lysozyme after entering the stationary phase.
On the other hand there are some pathogenic bacteria such as staphylococcus, which have the ability to develop a resistance strategy to lysozyme by producing a modified form of NAM (i.e. o-acetylated muramic acid). ...So is that the case during the late growth phase in the lysozyme-resistant grame +ve?
I agree with Vladislav. In addition, lysozyme needs five amino acid residues (Asp101, Gln57, Phe34, Asn37 and Arg114) to interact with unmodified PGN. I think, but it was unfortunately never checked, that the gene oatA (encoding this O-acetyltransferase) could be upregulated in the stationary phase to increase the O-acetylation grade of the PGN.
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