Abstract: The invention relates to a method for detecting the proportion of Gram-positive and Gram-negative bacteria in a complex sample. The bacteria are detected according to the Gram signal thereof. The invention enables distinction between species of Gram-positive bacteria and species of Gram-negative bacteria in a complex sample. The invention also relates to a kit for marking Gram-positive and Gram-negative bacteria, particularly for use in flow cytometry, particularly for complex samples such as human or animal microbiota samples.

Abstract: The present invention concerns a method for the screening of antibacterial substances comprising a step of determining the ability of a candidate substance to inhibit the activity of a purified enzyme selected from the group consisting of: (i) a D-aspartate ligase comprising a polypeptide having an amino acid sequence possessing at least 50% amino acid identity with an amino acid sequence selected from the group consisting of SEQ ID No 1 to SEQ ID No 10, or a biologically active fragment thereof; and (ii) a L,D-transpeptidase comprising a polypeptide having an amino acid sequence possessing at least 50% amino acid identity with the amino acid sequence of SEQ ID No 11, or a biologically active fragment thereof.