The resistance of microorganisms’ biofilms to antibacterials is a problem both for medicine and for many industries. Increasing the effectiveness of antimicrobial agents is an urgent task. The goal of the present work was to develop a new approach to development of anti-biofilm compositions based on conventional disinfectants in combination with enhancers (adjuvants). Methods of microbiology (viable cells count, model biofilms) and electron microscopy were employed. This research formulates the principles for selection of adjuvants. The adjuvants should: (1) increase the efficiency of decomposition of the biofilm matrix or/and (2) suppress the microbial protective mechanisms. For testing anti-biofilm compositions, two models of biofilms have been developed, on a solid surface at the interface with air or liquid. It was demonstrated that hydrogen peroxide, ethanol, isopropanol, and 4-hexylresorcinol enhanced the biocidal effect of disinfectants based on oxidants (peroxides and chlorine-containing) and quaternary ammonium salts by three to six orders of magnitude. Mechanisms of adjuvant action were mechanical decomposition of the matrix (by oxygen bubbles formed inside a biofilm in the case of hydrogen peroxide), coagulation of matrix polymers (in the case of alcohols), and a decrease in metabolism (in the case of 4-hexylresorcinol). The use of approved chemicals as adjuvants will accelerate the design of effective anti-biofilm antiseptics for medicine, social hygiene, and food manufactures and other industries.

Immobilized bacterial cells are presently widely used in the development of bacterial preparations for the bioremediation of contaminated environmental objects. Oil hydrocarbons are among the most abundant pollutants. We have previously described a new biocomposite material containing hydrocarbon-oxidizing bacteria (HOB) embedded in silanol-humate gels (SHG) based on humates and aminopropyltriethoxysilane (APTES); high viable cell titer was maintained in this material for at least 12 months. The goal of the work was to describe the ways of long-term HOB survival in SHG and the relevant morphotypes using the techniques of microbiology, instrumental analytical chemistry and biochemistry, and electron microscopy. Bacteria surviving in SHG were characterized by: (1) capacity for rapid reactivation (growth and hydrocarbon oxidation) in fresh medium; (2) ability to synthesize surface-active compounds, which was not observed in the cultures stored without SHG); (3) elevated stress resistance (ability to grow at high Cu2+ and NaCl concentrations); (4) physiological heterogeneity of the populations, which contained the stationary hypometabolic cells, cystlike anabiotic dormant forms (DF), and ultrasmall cells; (5) occurrence of piles in many cells, which were probably used to exchange genetic material; (6) modification of the phase variants spectrum in the population growing after long-term storage in SHG; and (7) oxidation of ethanol and acetate by HOB populations stored in SHG. The combination of the physiological and cytomorphological properties of the cells surviving in SHG for long periods may indicate a new type of long-term bacterial survival, i.e., in a hypometabolic state.