Growth and surface binding of proteins by Neisseria meningitidis in normal human serum

The addition of normal human serum to a chemically defined medium stimulated the growth of Neisseria meningitidis strain M1011 greatly. Both lag times and mean generation times were reduced. Growth in human serum alone was rapid but quickly became nutrientlimited. Iron was not a limiting factor for growth in human serum. One major limiting factor of serum was cysteine. N. meningitidis grown in serum also bound serum proteins, including transferrin and immunoglobulin, as demonstrated by direct and indirect fluorescent-antibody techniques.