physiologic saline was used for Bacteria dilutions , It content 0.85 gm from NaCl in 100 ml D. water or pepton water using in Bacteria dilutions, It was prepared 0.1 gm in 100 D. water.
But phosphate buffered saline are found more types and used in more methods Exp. Enzymatic methods , DNA extract . The types of phosphate buffered saline was different in contents but no used in Bacteria dilutions .
The best dilution solution is MRD - Maximum Recovery diluent. It is basically saline with 0.1 % peptone as a carbon source. Provides the perfect osmotic support necessary for small interval manipulation
I agree with Mary, saline without peptone may not be suffcient for the recovery of microorganisms because it may cause osmotic stress. Personally I use Maximum Recovery Diluent (Oxoid) - 0.45% NaCl and 0.45% peptone. If you need to recover microorganisms from feaces phospahte buffered saline should be better. You can check the description of the whole procedure in: ''Bacterial, SCFA and gas profiles of a range of food ingredients following in vitro fermentation by human colonic microbiota''.