A thorough investigation of dynamical chiral symmetry breaking in the quark-gluon interaction of quenched Landau gauge QCD is performed. The coupled dynamical system of Dyson-Schwinger equations for the quark-gluon vertex and determined self consistent solutions both analytically and numerically are considered. The most important results are:
(a) an overall as well as collinear infrared divergence of the vertex scaling is found;
(b) this infrared divergence implies an infrared-divergent running coupling in contrast to the infrared-finite fixed point behaviors of the coupling in the Yang-Mills sector of the theory;
(c) the collinear infrared divergence triggers an infrared-divergent one-gluon exchange kernel between two quarks, leading to a linear rising static quark potential which implies quark confinement;
(d) if chiral symmetry is restored by hand it is found a different self- consistent solution of the quark propagator and vertex Dyson-Schwinger equations: the vertex then has an infrared singularity which is reduced in strength compared to the chirally broken case;
(e) this reduced infrared strength in the chirally symmetric case leads an infrared constant coupling from the quark-gluon vertex and to a Coulomb-type static quark-antiquark potential, which is not confining. One of the important findings that is reported in the paper is that quark-gluon vertex has a considerable strength in the infrared. In particular infrared singularities arise not only in the uniform limit when all external momenta tend to zero, but also when only the gluon momentum vanishes.