Synergy

SYNERGY, the ability to combine individual elementary movements into a complex motor act. The most illustrative example of synergy is the associated movements of the musculature directed toward maintaining the body's equilibrium in all its diverse positions. For details and literature, see Movements, Cerebellum, Muscular system. In microbiology, synergy refers to the cooperation of microbes in a plant or animal organism when it is infected by two or more species of bacteria or protozoa. Synergy is the opposite of antagonism (see), in which different species of microbes in a plant or animal organism enter into a struggle with each other aimed at mutual destruction. Synergy and antagonism of microbes in vivo correspond to their symbiosis (see) and antibiosis in vitro in their mixed cultures on a dead nutrient substrate. The first observations in the field of synergy, as well as other indicated forms of microbial associations, belong to Pasteur (Pasteur, 1863), who showed that the epidemic disease of silkworms represents two different infections (pebrine—la pebrine and flacherie—la flacherie), caused by two different parasites and often developing together in one and the same silkworm. The first systematic studies in the field of microbial associations, including synergy, were made by Garré (Garré, 1887). Since that time, numerous works have shown the enormous importance of these associations in pathology, hygiene, agronomy, and in technical and industrial microbiology. Aerobes and anaerobes enter into synergistic combinations. From numerous examples, the following can be pointed out. Streptococcus, even having lost its virulence, in combination with saprophytes (see) Bac. mucoides, Bac. mesentericus, Bac. anthracoides kills a guinea pig, and sharply intensifies the pathogenic effect of the plague bacillus, Pfeiffer's influenza bacillus, the diphtheria bacillus, and many others. The virulence of the tuberculosis bacillus increases when it is introduced into animals together with streptococci and staphylococci. Experimental tetanus proceeds more severely in animals if a culture of the tetanus bacillus is introduced together with Bac. acidi lactici, Bac. prodigiosus, Bac. proteus vulgaris. According to the observations of Weinberg and Séguin (1916–18), the anaerobes Bac. perfringens and Bac. sporogenes increase their virulence for guinea pigs in combination with the anaerobe Bac. histolyticus or even with the aerobic saprophyte Bac. anthracoides. According to the experiments of Kompaneets, Dmitrieva, and Nikolskaya (1932), typhoid and staphylococcal vaccines enhance the effect of the smallpox vaccine, etc. From the examples cited, it is evident what practical significance synergy can have when it is necessary to enhance a culture or its immunizing effect. The essence and mechanism of synergy have not been clarified in view of the extreme complexity of this phenomenon. It is assumed that the synergistic interaction of microbes may depend on their characteristic enzymes, metabolic products, changes produced in the organism infected by them, etc. Synergy is considered unilateral when one participant stimulates the action of the other, or bilateral when both participants mutually enhance the pathogenic properties they possess. However, in each individual case, it is not always possible to establish whether it is a matter of unilateral or bilateral synergy.