Effects of the culture conditions on the growth and auto-aggregation ability of vaginal Lactobacillus johnsonii CRL 1294

MARÍA SILVINA JUÁREZ TOMÁS; MARÍA ELENA NADER-MACÍAS; BIRGITT WIESE

Badajoz. España

Conferencia; 1 st International Conference on Environmental, Industrial and Applied Microbiology; 2005

Universidad de Extremadura. Formatex Research Center (Badajoz)

The auto-aggregation ability, or formation of multicellular clumps between micro-organisms of the same strain, is one of the proposed mechanism to explain the protective role of lactobacilli in the human vagina. This property, related to the adhesion ability to epithelial vaginal cells, could promote to lactobacilli the formation of a biofilm on the vaginal epithelia, preventing of entry of pathogens [1]. The biochemical characterization of the aggregation-promoting factors of lactobacilli from different origins was performed subjecting the microbial cells or the culture supernatant at different treatments (pH, temperatures, enzymes, etc.). However, the effect of several culture conditions on the auto-aggregation phenomenon was not deeply evaluated until now. The auto-aggregation of different vaginal lactobacilli isolated from women of Tucumán, Argentina, was reported previously [2]. Among those lactobacilli, Lactobacillus johnsonii CRL 1294 presented a remarkable auto-aggregating pattern associated to a protein factor of the bacterial cellular surface, being a candidate to be included in a vaginal probiotic formula. The objectives of the present paper were to determine the optimal growth conditions and to evaluate the effect of different physicochemical factors on the auto-aggregating ability of L. johnsonii CRL 1294. L. johnsonii CRL 1294 was cultivated in LAPTg and MRS broth, at different initial pH (5, 6.5 or 8) and temperature of incubation (30, 37 or 44°C). The growth parameters were estimated by the Gompertz model from absorbance data, and they were affected in a different way by the physicochemical factors tested. The growth media affected significantly the increase of biomass and the growth rate, and the temperature exerted statistically significant effects on the final biomass and lag phase. However, the initial pH of the culture media only affected the duration of the lag phase. The optimal growth of L. johnsonii CRL 1294 (values of increase of biomass close to 2.0; growth rate of 0.21-0.27 h-1 and lag phase of 2.5 h) was reached at an initial pH 6.5 and at temperature of 37ºC, both in LAPTg and MRS. The auto-aggregation was quantitatively determined [3] and the auto-aggregation parameters were estimated by applying a model of exponential association proposed in this work. The auto-aggregation ability was evidenced in all the growth phases, being higher at pH 5 or 6.5 (76-88%). The higher cellular aggregation evidenced at low pH could be a fundamental characteristic in the acidic vaginal environment to promote the protective role of lactobacilli.