Evidence for an autocrine/paracrine function of chorionic gonadotropin in Xanthomonas maltophilia.

In the human and all other mammalian systems studied, LH and hCG bind to a common high affinity receptor with equal affinity. We have recently reported that a unique high affinity binding site in Xanthomonas maltophilia preferentially binds hCG and a native CG-like ligand over LH or other glycoprotein hormones. In the current studies, we have analyzed the effect of hCG or the native ligand on culturing Xanthomonas maltophilia. Both the human and native ligand caused a dose-dependent alteration in the pattern of the growth cycle and a change in the morphology of the bacteria during the stationary phase of the growth cycle. The protein concentration reached during the stationary phase was significantly (P < 0.005) higher in cultures supplemented with hCG or the native ligand. When an aliquot of the culture was diluted and plated on Earl's Martin Balanced agar plates, the number of subsequent colonies was increased (P < 0.02) in the fractions supplemented with the ligands. The increased growth was significant (P < 0.05) to the lowest concentration of 50 ng/ml ligand. When grown under partially anaerobic conditions, the effects of hCG were observed earlier in the growth cycle. The active hormones, hCG and native ligand, also changed bacterial morphology. These data indicate that hCG may have an autocrine and/or paracrine function in bacteria.