Estimation of vaginal probiotic lactobacilli growth parameters with the application of the Gompertz model

Integrated phenotypic-genotypic approach to understand the influence of ultrasound on metabolic response of Lactobacillus sakei

The lethal effects of soundwaves on a range of microorganisms have been known for almost a century whereas, the use of ultrasound to promote or control their activity is much more recent. Moreover, the fundamental molecular mechanism influencing the behaviour of microorganisms subjected to ultrasonic waves is not well established. In this study, we investigated the influence of ultrasonic frequencies of 20, 45, 130 and 950 kHz on growth kinetics of Lactobacillus sakei. A significant increase in the growth rate of L. sakei was observed following ultrasound treatment at 20 kHz despite the treatment yielding a significant reduction of ca. 3 log cfu/mL in cells count. Scanning electron microscopy showed that ultrasound caused significant changes on the cell surface of L. sakei culture with the formation of pores "sonoporation". Phenotypic microarrays showed that all ultrasound treated L. sakei after exposure to various carbon, nitrogen, phosphorus and sulphur sources had significant variations in nutrient utilisation. Integration of this phenotypic data with the genome of L. sakei revealed that various metabolic pathways were being influenced by the ultrasound treatments. Results presented in this study showed that the physiological response of L. sakei in response to US is frequency dependent and that it can influence metabolic pathways. Hence, ultrasound treatments can be employed to modulate microbial activity for specialised applications.

Lactic Acid Bacteria from Argentinean Fermented Foods: Isolation and Characterization for their Potential Use as Starters for Fermentation of Vegetables

Lactic acid bacteria (LAB) improve the organoleptic, nutritional and physicochemical properties of artisanal foods. In this study, we selected 31 fermented dairy and vegetable foods marketed in Tucumán city, Argentina, as sources of LAB for the production of pickles. Sixty-four isolates presumptively identified as Lactobacillus strains were screened for relevant technological properties for production of fermented foods. Most strains showed moderate to good acidification (>0.04 pH units/h) and proteolytic capabilities (free aminoacids >1 mmol/L), produced diacetyl and/or acetoin and were resistant to 4% NaCl. Based on acid production and osmotolerance, we selected six LAB strains and identified them by 16S rDNA sequencing (97–100% identity) as: Lactobacillus rhamnosus CRL2159 and CRL2164, L. plantarum CRL2161 and CRL2162, Weissella viridescens CRL2160 and W. paramesenteroides CRL2163. Relevant properties for pickle manufacturing were further assessed. At an initial pH=4.5 and 7% NaCl, L. plantarum CRL2162 and L. rhamnosus CRL2164 performed the best with high growth and inhibitory activity against Escherichia coli and Listeria innocua. There was no obvious antagonism among the selected strains that would dismiss their use in mixed cultures. Properties of the selected LAB suggest their potential as starter cultures for obtaining standardized, fermented vegetable products of high quality. The development of these new industrial starters would increase the competitiveness of production and open the country’s frontiers in the canned vegetable market.

Bioremediation technologies for polluted seawater sampled after an oil-spill in Taranto Gulf (Italy): A comparison of biostimulation, bioaugmentation and use of a washing agent in microcosm studies

One of the main challenges of bioremediation is to define efficient protocols having a low environmental impact. We have investigated the effect of three treatments in oily-seawater after a real oil-spill occurred in the Gulf of Taranto (Italy). Biostimulation with inorganic nutrients allowed the biodegradation of the 73±2.4% of hydrocarbons, bioaugmentation with a selected hydrocarbonoclastic consortium consisting of Alcanivorax borkumensis, Alcanivorax dieselolei, Marinobacter hydrocarbonoclasticus, Cycloclasticus sp. 78-ME and Thalassolituus oleivorans degraded 79±3.2%, while the addition of nutrients and a washing agent has allowed the degradation of the 69±2.6%. On the other hand, microbial community was severely affected by the addition of the washing agent and the same product seemed to inhibit the growth of the majority of strains composing the selected consortium at the tested concentration. The use of dispersant should be accurately evaluated also considering its effect on the principal actors of biodegradation.

Alcanivorax borkumensis produces an extracellular siderophore in iron-limitation condition maintaining the hydrocarbon-degradation efficiency

Obligate marine hydrocarbonoclastic bacteria possess genetic and physiological features to use hydrocarbons as sole source of carbon and to compete for the uptake of nutrients in usually nutrient-depleted marine habitats. In the present work we have studied the siderophore-based iron uptake systems in Alcanivorax borkumensis SK2 and their functioning during biodegradation of an aliphatic hydrocarbon, tetradecane, under iron limitation conditions. The antiSMASH analysis of SK2 genome revealed the presence of two different putative operons of siderophore synthetases. Search for the predicted core structures indicated that one siderophore is clearly affiliated to the family of complex oligopeptidic siderophores possessing an Orn-Ser-Orn carboxyl motif whereas the second one is likely to belong to the family of SA (salicylic acid)-based siderophores. Analyzing the supernatant of SK2 culture, an extracellular siderophore was identified and its structure was resolved. Thus, along with the recently described membrane-associated amphiphilic tetrapeptidic siderophore amphibactin, strain SK2 additionally produces an extracellular type of iron-chelating molecule with structural similarity to pseudomonins. Comparative Q-PCR analysis of siderophore synthetases demonstrated their significant up-regulation in iron-depleted medium. Different expression patterns were recorded for two operons during the early and late exponential phases of growth, suggesting a different function of these two siderophores under iron-depleted conditions.

Optimisation of batch culture conditions for cell-envelope-associated proteinase production from Lactobacillus delbrueckii subsp. lactis ATCC® 7830™

Using a combination of conventional sequential techniques, the batch growth conditions for the production of cell-envelope-associated proteinases have for the first time been studied and optimised in Lactobacillus delbrueckii subsp. lactis 313 (ATCC 7830; LDL 313). Concentrations of inoculum (0.1 < X < 10 % vol/vol), agitation speed (0 < S < 200 rpm), varying incubation temperature (30 < T < 50 °C), starting pH (4.5 < pH < 7) and carbon/nitrogen ratio of production medium (0.2 < r < 5) had an individual effect on proteinase yield (p < 0.01). Optimal conditions for proteinase production included an initial pH of 6.0, 45 °C incubation temperature, 2 % (v/v) inoculum size of OD(560) = 1, 150 rpm agitation speed, and growth medium carbon/nitrogen ratio of 1.0. Maximum proteinase activity obtained for whole cells was 0.99 U/ml after 8 h of incubation. The variables studied are very relevant due to their significance in improving the productivity of proteinase synthesis from LDL 313, under process and, likely, economic optimum conditions.

Lactobacillus acidophilus contributes to a healthy environment for vaginal epithelial cells

Lactobacillus species in the female genital tract are thought to act as a barrier to infection. Several studies have demonstrated that lactobacilli can adhere to vaginal epithelial cells. However, little is known about how the adherence of lactobacilli to vaginal epithelial cells affects the acidity, cell viability, or proliferation of the lactobacilli themselves or those of vaginal epithelial cells. Lactobacillus acidophilus was co-cultured with immortalized human vaginal epithelial cells (MS74 cell line), and the growth of L. acidophilus and the acidity of the culture medium were measured. MS74 cell density and viability were also assessed by counting cell numbers and observing the cell attachment state. L. acidophilus showed exponential growth for the first 6 hr until 9 hr, and the pH was maintained close to 4.0-5.0 at 24 hr after culture, consistent with previous studies. The growth curve of L. acidophilus or the pH values were relatively unaffected by co-culture with MS74 cells, confirming that L. acidophilus maintains a low pH in the presence of MS74 cells. This co-culture model could therefore potentially be used to mimic vaginal conditions for future in vitro studies. On the other hand, MS74 cells co-cultured with L. acidophilus more firmly attached to the culture plate, and a higher number of cells were present compared to cells cultured in the absence of L. acidophilus. These results indicate that L. acidophilus increases MS74 cell proliferation and viability, suggesting that lactobacilli may contribute to the healthy environment for vaginal epithelial cells.

Stability of freeze-dried vaginalLactobacillusstrains in the presence of different lyoprotectors

The industrial use of lactic acid bacteria as probiotic cultures depends on the preservation techniques employed, which are required to guarantee stable cultures in terms of viability and functional activity. The aim of this study was to evaluate the effects of 12% lactose and 12% sucrose suspended in water or reconstituted skim milk on the survival and expression of beneficial characteristics during freeze-drying and subsequent storage of 6 vaginal lactobacilli strains. A cubic polynomial model was also used for the first time to evaluate the effects of different protectors on survival behavior during storage. Different survival patterns were observed among the strains considered. The presence of both lactose and sucrose in water or in 6% skim milk as the suspension medium proved to be effective in maintaining a high degree of survival and expression of potentially probiotic characteristics (production of antimicrobial substances or auto-aggregation capabilities) of most strains after lyophilization and long-term storage. This study constitutes a valuable step to obtain concentrated cultures with the highest stability of microorganisms for pharmaceutical purposes.

Viability of vaginal probiotic lactobacilli during refrigerated and frozen storage

The viability of six different strains of probiotic vaginal Lactobacillus was examined in two different cryoprotective media, during refrigerated versus frozen storage, and using two traditional types of stock cultures for starting the biomass production. Freezing at -20 degrees C and -70 degrees C had much less adverse effect on viability than did storage at 7 degrees C, and the reduction in viability was greater at -20 degrees C than at -70 degrees C. The strains showed variation in the extent of the viability losses during both types of storage. Milk-yeast extract (MYE) was shown to be the more suitable protective medium to maintain viability of the strains during the storage. The vaginal Lactobacillus strains are most stable in MYE at -70 degrees C with only a small decrease of the viability observed under these conditions. The viable cell counts of Lactobacillus paracasei CRL 1251 and CRL 1289, L. crispatus CRL 1266 and L. salivarius CRL 1328 remained around 1 x 10(8) CFU/mL after 24 months of storage at -70 degrees C, or up to 18 months for L. acidophilus CRL 1259.

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

AIMS

To evaluate the effects of different physico-chemical factors on the growth and auto-aggregating ability of vaginal Lactobacillus johnsonii CRL 1294.

METHODS AND RESULTS

L. johnsonii CRL 1294 was cultivated in different culture media, initial pH and temperature of incubation. The growth parameters were estimated by the Gompertz model, being optimal (higher final biomass and growth rate, and shorter lag phase) at an initial pH of 6.5 and at a temperature of 37 degrees C, both in LAPTg and MRS. The auto-aggregation ability, which was assessed by a model of exponential association, was evidenced in all the growth phases, being higher at pH 5 or 6.5.

CONCLUSIONS

The growth of L. johnsonii CRL 1294 was affected in different way by all the physico-chemical factors tested. However, the auto-aggregation ability increased mainly at low initial pH of growth media.

SIGNIFICANCE AND IMPACT OF THE STUDY

The auto-aggregation ability under different culture conditions of a vaginal Lactobacillus strain was systematically and statistically evaluated for the first time. 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.

Inhibitory effect of sodium fluoride and chlorhexidine on the growth of oral lactobacilli

The accumulation of microorganisms in dental plaque is related to the etiology of caries and periodontal disease, with a high prevalence worldwide. The prophylactic measures include the use of chemical agents as NaF and chlorhexidine. Lactic acid bacteria are members of the normal microbiota of the oral cavity being discussed with regard to their beneficial or detrimental effect in this environment. The present study was performed to determine the growth of some species of Lactobacillus at different concentrations of NaF and chlorhexidine. The strains were isolated from both caries-free and caries patients. Their growth parameters were evaluated by the application of the Gompertz model to the experimental data of optical density as a measurement of growth. The degree of inhibition of the growth of all of the lactobacilli studied was different, depending on each particular strain. NaF at 1 mmol x L(-1) inhibited between 5% and 46%, at 5 mmol x L(-1) between 13% and 65%, and at 20 mmol x L(-1) between 57% and 84%. CHX at higher concentrations (197 and 98 mmol x L(-1) showed a complete inhibition of some of the strains. The significance of the results was evaluated by the application of a multivariate analysis and also compared with the inhibition of pathogenic Streptococcus mutans and with lactobacilli strains from collection cultures.

Prebiotic effects of oligosaccharides on selected vaginal lactobacilli and pathogenic microorganisms

The purpose of this study was to select endogenous human vaginal lactobacilli strains on the basis of the main probiotic properties observed in the vaginal environment in order to use them for the evaluation of the potential prebiotic properties of oligosaccharides. From vaginal samples of 50 women with a normal flora, 17 lactobacilli strains were first isolated because of their high level of hydrogen peroxide production. Then six strains were selected mainly for their ability (i) to adhere to vaginal cells, (ii) to produce compounds in sufficient amount, such as lactic acid, having an inhibitory action on pathogens, and less importantly, (iii) to demonstrate arginine deiminase activity. These six strains were found to belong to three distinct species: Lactobacillus crispatus, L. jensenii and L. vaginalis. One strain of each species was chosen as a potential vaginal probiotic strain with regard to our criteria. These three strains were then used to evaluate the prebiotic properties of different oligosaccharide series: two fructooligosaccharide series (FOS Actilight and FOS Raftilose) and two glucooligosaccharide series varying by their osidic linkages (alpha-1,6/alpha-1,4 GOS and alpha-1,2/alpha-1,6/alpha-1,4 GOS). The test was based on the ability of the oligosaccharides to promote the growth of the three beneficial strains selected but not of pathogenic microorganisms often encountered in urogenital infections such as Candida albicans, Escherichia coli and Gardnerella vaginalis. Oligosaccharide hydrolysis was followed by HPLC analysis. This revealed that two oligosaccharide series (FOS Actilight DP3 and all alpha-1,6/alpha-1,4 GOS DP > or = 4) were used only by the lactobacilli strains, the pathogenic microorganisms being unable to metabolise them. The selected lactobacilli and oligosaccharides are good candidates for incorporation in a formula to prevent vaginal infections.

Growth and lactic acid production by vaginal Lactobacillus acidophilus CRL 1259, and inhibition of uropathogenic Escherichia coli

Lactic acid-producing lactobacilli were selected from 134 human vaginal isolates by testing their capability to inhibit the growth of different pathogenic micro-organisms. Lactobacillus acidophilus CRL 1259 (from the CERELA Culture Collection) was selected to study the effects of temperature, pH and culture medium on growth and lactic acid production. Growth parameters were estimated by using the model of Gompertz. Kinetics of inhibition of uropathogenic Escherichia coli were evaluated in mixed cultures of the pathogen and L. acidophilus. Optimal conditions for growth and lactic acid production by L. acidophilus were pH 6.5 or 8.0 and 37 degrees C. Under these conditions, growth was higher in LAPTg (yeast extract/peptone/tryptone/Tween 80/glucose) broth than in MRS (De Man-Rogosa-Sharpe) broth. However, lactic acid production was more efficient in MRS broth. Under optimal conditions for lactic acid production, L. acidophilus inhibited the growth of E. coli. These results suggest that inclusion of L. acidophilus CRL 1259 in probiotic products for vaginal application would be beneficial.

Comparison of the growth and hydrogen peroxide production by vaginal probiotic lactobacilli under different culture conditions

OBJECTIVE

The purpose of this study was to determine the optimal conditions for the growth and hydrogen peroxide production by vaginal lactobacilli.

STUDY DESIGN

Two vaginal lactobacillus strains were cultured under different growth conditions (temperature, pH, agitation, and growth media) with a fractional factorial experimental design.

RESULTS

The optimal growth conditions of Lactobacillus paracasei CRL (Centro de Referencia para Lactobacilus Culture Collection) 1289 and Lactobacillus crispatus CRL 1266 were temperature 37 degrees C and initial pH 6.5, nonagitated cultures, in autolysat de levure; peptone, tryptone, Tween 80 et glucose (LAPTg) broth for L paracasei or in de Man-Rogosa-Sharpe (MRS) and LAPTg broths for L crispatus. The hydrogen peroxide production, detected only in agitated cultures, was higher at 37 degrees C and pH 6.5. The oxidative metabolite produced the self-inhibition of the lactobacilli growth. In mixed cultures of lactobacilli and Staphylococcus aureus under the optimal conditions of hydrogen peroxide production, the pathogen growth was inhibited.

CONCLUSION

The results provided information about the factors that affect the hydrogen peroxide production and about the most favorable conditions with which to obtain the highest biomass in the shortest possible time.

Influence of pH, temperature and culture media on the growth and bacteriocin production by vaginal Lactobacillus salivarius CRL 1328

AIMS

To study the influence of pH, temperature and culture medium on the growth and bacteriocin production by vaginal Lactobacillus salivarius subsp. salivarius CRL 1328.

METHODS AND RESULTS

The study was performed using a complete factorial experimental design. Lactobacillus salivarius was cultivated in LAPTg and MRS broths, adjusted to specific initial pH, and at different temperatures of incubation. The growth, which was evaluated by the Gompertz model, was higher in MRS broth than in LAPTg broth. The initial pH of the culture medium and the temperature had a dramatic effect on the production of bacteriocin. The optimal conditions for bacteriocin production were different to those for optimal growth. The decrease in the pH of the culture medium was parallel to the growth; pH had similar final values in both the MRS and the LAPTg broths.

CONCLUSIONS

The optimal growth conditions were recorded in MRS broth, with an initial pH of 6.5 and a temperature of 37 degrees C. The maximum bacteriocin activity was obtained in LAPTg after 6 h at 37 degrees C, and at an initial pH of 6.5 or 8.0.

SIGNIFICANCE AND IMPACT OF THE STUDY

The application of a complete factorial design, and the evaluation of the growth parameters through the Gompertz model, enabled a rapid and simultaneous exploration of the influence of pH, temperature and growth medium on both growth and bacteriocin production by vaginal Lact. salivarius CRL 1328.