Potential of Pediococcus pentosaceus (L006) isolated from maize leaf to suppress fumonisin-producing fungal growth.

The present study was aimed at characterizing the ability of lactic acid bacteria isolated from maize to repress the growth of fumonisin-producing fungi. A total of 67 isolates were screened for their antifungal activity against Fusarium proliferatum and Fusarium verticillioides by using the overlay method. The most efficient antifungal isolate was identified as Pediococcus pentosaceus (L006), on the basis of physiological and biochemical characterization and 16S rRNA gene sequencing. Production of the antifungal metabolite by this isolate commenced at the end of the growth exponential phase (8 h) and reached a maximum level after a long period of incubation (120 h). The antifungal metabolites produced were shown to be heat stable, resistant to proteolytic enzyme treatments, and pH dependent. The exact chemical nature of these substances remains to be clarified.

Myocardial and interstitial matrix metalloproteinase activity after acute myocardial infarction in pigs.

A structural event during the evolution of a myocardial infarction (MI) is left ventricular (LV) remodeling. The mechanisms that contribute to early changes in LV myocardial remodeling in the post-MI period remain poorly understood. Matrix metalloproteinases (MMPs) contribute to tissue remodeling in several disease states. Whether and to what degree MMP activation occurs within the myocardial interstitium after acute MI remains to be determined. Adult pigs (n = 15) were instrumented to measure regional myocardial function and interstitial MMP levels within regions served by the circumflex and left anterior descending arteries. Regional function was measured by sonomicrometry, and interstitial MMP levels were determined by selective microdialysis and zymography as well as by MMP interstitial fluorogenic activity. Measurements were performed at baseline and sequentially for up to 3 h after ligation of the obtuse marginals of the circumflex artery. Regional fractional shortening fell by over 50% in the MI region but remained unchanged in the remote region after coronary occlusion. Release of soluble MMPs, as revealed by zymographic activity of myocardial interstitial samples, increased by 2 h post-MI. The increased zymographic activity after MI was consistent with MMP-9. Myocardial interstitial MMP fluorogenic activity became detectable within the ischemic region as early as 10 min after coronary occlusion and significantly increased after 1 h post-MI. MMP fluorogenic activity remained unchanged from baseline values in the remote region. The present study demonstrated that myocardial MMP activation can occur within the MI region in the absence of reperfusion. These unique results suggest that MMP release and activation occurs within the ischemic myocardial interstitium in the early post-MI period.

Evidence for a bacteriocin-like substance produced by a new strain of Streptococcus sp., inhibitory to gram-positive food-borne pathogens.

A new strain of Streptococcus sp. (CNCM I-841) isolated from a commercial probiotic product was shown to be antagonistic towards several food-borne pathogens including Clostridium sp. and Listeria monocytogenes. This strain produced and excreted an antibacterial substance in MRS broth. The inhibitory substance was different from hydrogen peroxide, since it was unaffected by catalase. It was sensitive to proteolytic enzymes, indicating that the active moiety of the inhibitor was proteinaceous in nature, and it had no effect on its producer strain. These properties suggested that the inhibitory substance could be considered as a bacteriocin-like substance. The antimicrobial substance was also produced in M17 and tryptose broths if they were supplemented with Tween-80. Partial purification allowed a 10.5-fold increase in the specific activity. A preliminary characterization showed that it was active against lactobacilli, Enterococcus faecalis, Clostridium sp. and Listeria sp. It was not affected by 2-h treatment at 60 degrees C, but was sensitive to treatments at 100 degrees C and to autoclaving at 121 degrees C. The activity was not affected by treatments at pH values ranging from 2 to 11.

Distribution of pathogen inhibition in the Lactobacillus isolates of a commercial probiotic consortium.

Pure strains of Lactobacillus ssp. isolated from a commercial probiotic consortium were checked in a double layer solid medium for their inhibition activities against selected pathogenic bacteria including serotypes of Listeria monocytogenes, Escherichia coli and Salmonella. The antagonistic properties of the Lactobacillus strains may be related to the production of bacteriocin-like compounds. All the pathogens tested were inhibited by one or a few strains of Lactobacillus, the best inhibition was observed against L. monocytogenes but the inhibition was also satisfactory against E. coli, Salm. typhimurium and Salm. enteritidis.

Bacterial degradation of ammonium lignosulfonate.

Bacterial strains were selected for their capacity to assimilate and to transform ammonium-lignosulfonate. Modification of the methyl content and of low molecular weight alkyl functions were demonstrated by gas-chromatography and HLPC analysis. Most of these strains completely degraded simple phenolic compounds related to lignosulfonate without inhibition by the carbohydrates present in the liquor. Further investigation suggested that the enzymes involved in the fission of the aromatic nuclei were constitutive in the strains tested.

Bacteriology and nutrition of environmental strains of Klebsiella pneumoniae involved in wood and bark decay.

Strains of Klebsiella pneumoniae were isolated from screening procedures for wood- and bark-decaying bacteria. Their bacteriological and biochemical properties, their sensitivity to antibiotics and assimilation of wood components were analysed. Most were pectinolytic, degraded xylan and different phenolic compounds. Unusual associations of capsular polysaccharides and biotypes were observed. The nitrogen fixation ability of these strains was also tested.

[Screening for cellulolytic bacteria with the cellulose-azure test (author's transl)]. / Recherche de bactéries cellulolytiques par la méthode à la cellulose-azur.

As the classical methods involving the clearing of opaque cellulose-agar media are not satisfying, a simple method utilizing cellulose-azure as a substrate has been adapted to detect cellulolytic activity of bacteria. This precise method may be combined with a primary growth on carboxymethyl-cellulose-agar to screen for cellulase-producing strains.