A carregar...
Publicação
Peptidoglycan amidation of Staphylococcus aureus and bacteria cell physiology
| Nome: | Descrição: | Tamanho: | Formato: | |
|---|---|---|---|---|
| 31.79 MB | Adobe PDF |
Orientador(es)
Resumo(s)
Peptidoglycan is a highly dynamic macromolecule that undergoes several
secondary modifications during its biosynthesis. The MurT-GatD enzymatic complex is
necessary for the amidation of glutamate of the stem peptide of Staphylococcus aureus
peptidoglycan. This secondary modification influences critical processes of S. aureus,
such as growth rate, beta-lactam and lysozyme resistance. However, the mechanisms
through which it influences S. aureus physiology remain unknown.
In this study, several MRSA strains and respective murT-gatD mutants were
used. Since peptidoglycan is a surface-exposed macromolecule, we analyzed the
influence of peptidoglycan amidation on the modulation of the cell envelope, by
measuring the surface charge, through a cytochrome C association based method. For
all strains, peptidoglycan amidation was associated with a more positive surface charge.
Consequently, such impact could alter cell-cell aggregation and surface-adhesion
properties. Overall, amidation mutants showed either increased biofilm production or
formation of cell aggregates during planktonic growth; these two distinct phenotypes
seemed to be associated with the biofilm matrix composition of the parental strain. In
fact, amidation mutants of PIA-positive parental strains showed formation of cell
aggregates, whereas the ones of PIA-negative parental strains showed higher biofilm
production. Additionally, biofilm detaching assays showed that the composition of the
biofilm matrix is altered in response to lack of peptidoglycan amidation.
Peptidoglycan amidation was proposed to influence autolysis, by disturbing the
balance between the cell wall synthetic and hydrolytic machineries and/or by acting as a signal to regulate the activity of autolysins. Zymographic assays suggested that nonamidated peptidoglycan is a better substrate for autolysins. Moreover, these enzymes seemed to be less expressed/active in amidation mutants. Western Blot and promoter fusion assays confirmed that peptidoglycan amidation influences the autolytic system, as non-amidated mutants showed lower expression of ATL and SLEI autolysins.
Descrição
Palavras-chave
Staphylococcus aureus peptidoglycan amidation biofilms autolysis