Antibacterial Activity of Some Lactic Acid Bacteria Isolated from an Algerian Dairy Product

In the present study, the antibacterial effect of 20 lactic acid bacteria isolates from a traditional cheese was investigated. 6 isolates showed antibacterial effect against Gram positive bacteria. Streptococcus thermophilus T2 strain showed the wide inhibitory spectrum against the Gram positive bacteria. Growth and bacteriocin production profiles showed that the maximal bacteriocin production, by S. thermophilus T2 cells, was measured by the end of the late-log phase (90 AU ml−1) with a bacteriocine production rate of 9.3 (AU ml−1) h−1. In addition, our findings showed that the bacteriocin, produced by S. thermophilus T2, was stable over a wide pH range (4–8); this indicates that such bacteriocin may be useful in acidic as well as nonacidic food. This preliminarily work shows the potential application of autochthonous lactic acid bacteria to improve safety of traditional fermented food

Assessment of the effects of sulfate and nitrate on the temporal evolution of Klebsiella oxytoca and Staphylococcus aureus abundance under shaking conditions, in aquatic microcosm

Most chemicals in natural aquatic media can be assimilated by bacteria. The impact of various environmental conditions on this microbial process is not always clear. This study aimed at investigating changes in the abundance of Klebsiella oxytoca and Staphylococcus aureus under different shaking conditions, in aquatic microcosms containing nitrate and sulfate. Sodium chloride solution (8.5 g NaCl•L-1), and nitrate and sulfate solutions (0.005, 0.05, 0.5 and 5 g•L-1) containing bacteria were supplemented with tryptic peptone at a final concentration of 10 g•L-1. The solutions were incubated under shaking conditions (300, 350 and 400 rev•min-1). Bacteriological analyses were performed hourly over a 6-h period. During the first 3 h of incubation, results showed that the highest values of the apparent cell growth rates (CAGRs) with K2SO4 in pure cultures, at a shaking speed 400 rev•min-1, were 0.656 h-1 for S. aureus, and 0.364 h-1 for K. oxytoca. In mixed culture, the CAGR was 0.235 h-1 for S. aureus, and 0.388 h-1 for K. oxytoca, both recorded at 300 rev•min-1. With KNO3 in pure culture solutions, the CAGR was 0.353 h-1 for S. aureus at 300 rev•min-1, and 0.367 h-1 for K. oxytoca at 350 rev•min-1. In mixed culture it was 0.454 h-1 for S. aureus and 0.393 h-1 for K. oxytoca, both recorded at 350 rev•min-1. The highest value of the apparent cell inhibition rate (CAIR) for S. aureus was 0.520 h-1 in K2SO4 (5 g•L-1, 400 rev•min-1), and 0.115 h-1 in KNO3 (5 g•L-1, 300 rev•min-1). For K. oxytoca, it was 0.07 h-1 in K2SO4 in pure culture (0.05 g•L-1, 300 rev•min-1), and 0.044 h-1 in mixed culture (0.05 g•L-1, 350 rev•min-1). In KNO3 it was 0.239 h-1 in mixed culture (5 g•L-1, 300 rev•min-1). The growth and inhibition potentials of different microbial species were impacted by the chemical concentrations and the movement speeds.L’impact de diverses conditions environnementales sur l’assimilation bactérienne dans l’eau, des composés chimiques est peu connu. La présente étude a visé l’évaluation de la dynamique d’abondance de Klebsiella oxytoca et Staphylococcus aureus sous diverses conditions, en milieu aquatique microcosme contenant du sulfate ou nitrate. Des solutions du NaCl (8,5 g•L-1), sulfate et nitrate (0,005, 0,05, 0,5 et 5 g•L-1) contenant des cellules ont été enrichies à la peptone trypsique (concentration finale 10 g•L-1), puis incubées sous conditions dynamiques (300, 350 et 400 tr•min-1). Les analyses bactériologiques ont été effectuées pendant 6 h. Il ressort qu’au cours des trois premières heures d'incubation, le taux de croissance cellulaire apparent (TCCA) le plus élevé en culture pure, contenant du K2SO4, est de 0,656 h-1 pour S. aureus, et 0,364 h-1 pour K. oxytoca, enregistrés à 400 tr•min-1. En culture mixte, il est de 0,235 h-1 pour S. aureus, et 0,388 h-1 pour K. oxytoca, enregistrés à 300 tr•min-1. Avec du KNO3, en culture pure, le TCCA est de 0,353 h-1 pour S. aureus à 300 tr•min-1, et 0,367 h-1 à 350 tr•min-1 pour K. oxytoka. En culture mixte, il est de 0,454 h-1 pour S. aureus et 0,393 h-1 pour K. oxytoca, enregistrés à 350 tr•min-1. Le taux d’inhibition cellulaire apparent (TICA) le plus élevé de S. aureus est de 0,520 h-1 en présence du K2SO4 (5 g•L-1, 400 tr•min-1), et 0,115 h-1 en présence de KNO3 (5 g•L-1, 300 tr•min-1). Pour K. oxytoca, il est de 0,07 h-1 avec du K2SO4 en culture pure (0,05 g•L-1, 300 tr•min-1), et 0,044 h-1 en culture mixte (0,05 g•L-1, 350 tr•min-1). Avec du KNO3, il est de 0,239 h-1 en culture mixte (5 g•L-1, 300 tr•min-1). La croissance et l’inhibition des microorganismes sont affectées par les concentrations en sels et la vitesse de mouvements du milieu

The effect of preculture conditions on the culturability and viability of Aeromonas hydrophila when exposed to oligotrophic and cold stresses

International audienceThe aim of this study is to assess the relationship between pre-culture conditions and loss of culturability of Aeromonas hydrophila exposed to a nutrient deprivation and low temperature (4A degrees C). The present results show that the behavior of A. hydrophila, when exposed to nutritional deprivation and low temperature, depends on the pre-culture conditions. After a 60-days period of incubation in Filtered Sterilized Distilled Water (FSDW) at 4A degrees C no culturable cells were observed for cells with a pre-culture in a liquid culture medium whereas a cell density of 1.8 log CFU/ml was observed for the bacterium with a pre-culture on solid medium with cells fixed on cellulose nitrate membrane. Colony count of A. hydrophila cells with anaerobic pre-culture declined to 0 CFU/ml within 16 days of incubation in FSDW at 4A degrees C showing that the cells under these conditions are more sensitive to nutritional deprivation and low temperature than cells with a pre-culture under aerobic conditions. Our findings showed also no culturable cells, after 8 days of incubation in FSDW, for A. hydrophila with a pre-culture at 4A degrees C. Moreover the present study showed no recovered cells from non culturable A. hydrophila when the FSDW was supplemented by catalase or sodium pyruvate. However, the addition of oxyrase, to non culturable A. hydrophila cells, was found to allow the recovery of non culturable cells

Desarrollo, poscolonialismo y teor\ueda pol\uedtica

The main purpose of this investigation was to rank in the hierarchical order, some factors which may be predominant in the daily changes in the abundance of Enterobacteriaceae in wells, in equatorial area of Cameroon (Central Africa). Those factors included electrical conductivity, color, temperature, total suspended solids (TSS), pH, turbidity, CO2, NH4+ , BOD5, and the cell concentration at the initial moment. The water temperature ranged between 19 and 20 °C. The turbidity in wells varied from 1.2 to 103 FTU. The highest concentrations of TSS varied from 10 to 102 mg.L-1. The values of water color fluctuated between 37 and 494 PtCo. The pH ranged from 4.93 to 8.04. The highest concentrations of dissolved CO2 reached 15.84 mg.L-1 and the lowest value was 8.8 mg.L-1. The values of electrical conductivity fluctuated between 244 and 767 µS.cm-1. The concentrations of NH4+ varied from 2.42 to 10.2 mg.L-1. The BOD5 values ranged from 5 to 125 mg.L-1. The bacteria concentrations at the initial moments for the whole wells points varied from 1.30 to 5 log units.mL-1. After 2 h of incubation, it fluctuated between 1.30 and 5 log units.mL-1. After 4 h incubation, it fluctuated between 1.30 and 4.78 log units.mL-1. It ranged between 1.30 and 4.80 log units.mL-1, 1.30 and 4.78 log units.mL-1, 1.30 and 4.84 log units.mL-1, and 1.30 and 4.90 log units.mL-1 after 6 h, 8 h, 10 h and 12 h of incubation respectively. The cell abundance undergoes fluctuation during incubation in each wells point. The concentration of Enterobacteriaceae decreased during the first hours of incubation in most cases. The decrease was followed after a delay that varied according to the sampling campaign, with an increase of cell abundance. Using the power-law function, it was noted that the dominant factors in the daily changes of instantaneous cell abundances, in decreasing hierarchical order were NH4+ , pH, dissolved CO2, turbidity, color, total suspended solids, and the BOD5. The electrical conductivity and the concentration of cells at the initial moments played a minor role. It also let out that in natural aquatic systems all factors do not impact at the same time

SUCCES DE PARIS : N °4 / Lucienne DELYLE - André CLAVEAU - Marie-Josée NEUVILLE - Line RENAUD - Georges GUETARY - René-Louis LAFFORGUE - Mathé ALTERY et Robert OLIVIERI

Titre uniforme : [Gwendolina]Titre uniforme : [Mon p'tit bonheur = Joey's song]Titre uniforme : [A woman in love]Titre uniforme : [Buenas noches mi amor]Titre uniforme : [Buenas noches mi amor]Comprend : NON NE DIS PAS NON - BUENAS NOCHES MI AMOR - J'AURAIS AIME ETRE UN GARCON - M'AMIE - GWENDILONA - T'ES BATH MOME - DES YEUX D'AMOUREUSE - LE CANCRE - MON P'TIT BONHEUR - MERCI PARIS - DITES-MOI - QU'EST-CE QUE J'AI FAIT DIS-MOI - CA C'EST CHOUETTE - FRIPON - CARMELITA - MON AMOUR DU BOUT DU MONDEBnF-Partenariats, Collection sonore - BelieveContient une table des matière