A bacteriologist is a scientist who studies bacteria and their effects on living organisms. The crossword solutions for the term 'bacteriologist' include Petri (5 letters), Rene (4 letters), Pasteur (7 letters), Ehrlich (7 letters), Jonas (5 letters), Salk (4 letters), AGAR (4 letters), Aerobe (6 letters), Koch (4 letters), and Fleming (7 letters). These scientists have made significant contributions to the field of bacteriology, such as Julius Petri's invention of the Petri dish, Rene Dubos' discovery of the antibiotic tyrothricin, Louis Pasteur's development of the germ theory of disease, Paul Ehrlich's work on immunology, Selman Waksman's discovery of streptomycin, Jonas Salk's development of the polio vaccine, Robert Koch's discovery of the tuberculosis bacillus, and Alexander Fleming's discovery of penicillin.