Identification and preliminary characterization of external membrane-bound nuclease activities in Mycoplasma pulmonis

Area of Science:

• Microbiology
• Enzymology
• Molecular Biology

Background:

• Mycoplasma pulmonis is a common respiratory pathogen.
• Extracellular enzymes play crucial roles in bacterial pathogenesis and host interactions.
• The presence and function of cell surface enzymes in Mycoplasma species are not fully characterized.

Purpose of the Study:

• To investigate the presence and characteristics of DNase activity on the surface of Mycoplasma pulmonis.
• To determine the enzymatic nature and potential origin of the cell surface DNase.

Main Methods:

• Assessing DNase activity on intact Mycoplasma pulmonis cells.
• Enzyme characterization including heat stability, metal ion inhibition (EDTA, zinc chloride), and protease sensitivity (trypsin).
• Quantifying cell surface DNase activity relative to total cellular DNase activity.

Main Results:

• Mycoplasma pulmonis possesses substantial DNase activity exposed on its cell surface.
• The surface DNase activity is heat-labile (destroyed at 56°C) and inhibited by EDTA and zinc chloride.
• Treatment with trypsin eliminated surface DNase activity, which was regenerated upon incubation, suggesting a proteinaceous enzyme.
• Cell surface DNase accounts for 20% of the total DNase activity in M. pulmonis extracts.

Conclusions:

• The cell surface DNase of Mycoplasma pulmonis is an endonuclease with enzymatic properties similar to other bacterial DNases.
• The enzyme's location and characteristics suggest a role in extracellular DNA degradation, potentially influencing host-pathogen interactions or biofilm formation.