Antiviral Potential of Lactic Acid Bacteria and Their Bacteriocins

Emerging resistance to antiviral agents is a growing public health concern worldwide as it was reported for respiratory, sexually transmitted and enteric viruses. Therefore, there is a growing demand for new, unconventional antiviral agents which may serve as an alternative to the currently used drugs. Meanwhile, published literature continues shedding the light on the potency of lactic acid bacteria (LAB) and their bacteriocins as antiviral agents. Health-promoting LAB probiotics may exert their antiviral activity by (1) direct probiotic–virus interaction; (2) production of antiviral inhibitory metabolites; and/or (3) via stimulation of the immune system. The aim of this review was to highlight the antiviral activity of LAB and substances they produce with antiviral activity.     

Cellular Fatty Acid Composition and Identification of Rumen Bacteria

The fatty acid compositions of 21 pure cultures of rumen bacteria, representing 12 genera and 14 species, were compared as methyl esters. Each organism possessed a consistent and reproducible fatty acid profile. Overlapping similarities and differences in composition did not allow differentiation between families or genera. Although species differentiation was possible, fatty acid composition appeared to be only an aid in the identification of bacteria.     

乳酸菌作为口服疫苗载体的研究进展

乳酸菌是一类重要的工业菌株,是食品级安全菌。利用乳酸菌作为表达载体制成的口服疫苗安全无毒,乳酸菌口服疫苗通过胃肠粘膜进行抗原呈递,能诱导机体产生有效的免疫应答和免疫耐受。近年来对于乳酸菌口服疫苗的研究成为热点,并在此方面取得了突破性成果。     

Automated Systems for Identification of Heterotrophic Marine Bacteria on the Basis of Their Fatty Acid Composition

The fatty acid methyl ester composition of a total of 71 marine strains representing the genera Alteromonas, Deleya, Oceanospirillum, and Vibrio was determined by gas-liquid chromatographic analysis. Over 70 different fatty acids were found. The predominant fatty acids were 16:0, 16:1 cis 9, summed-in-feature (SIF) 4 (15:0 iso 2OH and/or 16:1 trans 9) and SIF 7 (18:1 cis 11, 18:1 trans 9, and/or 18:1 trans 6) for all the strains considered, but minor quantitative variations could be used to distinguish the different genera. In addition to a conventional statistical processing method to analyze the data and draw comparison between species and genera, an approach involving neutral network-based elaboration is applied. The statistical analysis and dendrogram representation gave a comparison of the species considered, while the neural network computation provided a more accurate assignment of species to their genera. Moreover, by using neural networks, it was possible to conclude that only 22 fatty acids were important for the identification of the marine genera considered. A database of Alteromonas, Deleya, Oceanospirillum, and Vibrio fatty acid methyl ester profiles was generated and is now routinely used to identify fresh marine isolates.     

Animal Rennets as Sources of Dairy Lactic Acid Bacteria

The microbial composition of artisan and industrial animal rennet pastes was studied by using both culture-dependent and -independent approaches. Pyrosequencing targeting the 16S rRNA gene allowed to identify 361 operational taxonomic units (OTUs) to the genus/species level. Among lactic acid bacteria (LAB), Streptococcus thermophilus and some lactobacilli, mainly Lactobacillus crispatus and Lactobacillus reuteri, were the most abundant species, with differences among the samples. Twelve groups of microorganisms were targeted by viable plate counts revealing a dominance of mesophilic cocci. All rennets were able to acidify ultrahigh-temperature-processed (UHT) milk as shown by pH and total titratable acidity (TTA). Presumptive LAB isolated at the highest dilutions of acidified milks were phenotypically characterized, grouped, differentiated at the strain level by randomly amplified polymorphic DNA (RAPD)-PCR analysis, and subjected to 16S rRNA gene sequencing. Only 18 strains were clearly identified at the species level, as Enterococcus casseliflavus, Enterococcus faecium, Enterococcus faecalis, Enterococcus lactis, Lactobacillus delbrueckii, and Streptococcus thermophilus, while the other strains, all belonging to the genus Enterococcus, could not be allotted into any previously described species. The phylogenetic analysis showed that these strains might represent different unknown species. All strains were evaluated for their dairy technological performances. All isolates produced diacetyl, and 10 of them produced a rapid pH drop in milk, but only 3 isolates were also autolytic. This work showed that animal rennet pastes can be sources of LAB, mainly enterococci, that might contribute to the microbial diversity associated with dairy productions.     

乳酸菌酸胁迫反应机制研究进展

乳酸菌可发酵糖类产生乳酸,并广泛应用于食品、药物和饲料等工业。由于有机酸的积累,乳酸菌大部分的生长代谢都在低pH的酸性环境中进行,具有酸胁迫反应。pH的自我平衡、ATR反应机制、对大分子的保护和修复作用及细胞膜的变化等是乳酸菌酸胁迫反应的主要机制,其中,pH自我平衡包括F0F1-ATPase质子泵、精氨酸脱氨酶途径(ADI)和谷氨酸脱羧酶途径(GAD)等。由此可见,乳酸菌酸胁迫反应机制涉及到基因和蛋白的表达调控等,是非常复杂的网络调控体系。     

Lactic Acid Bacteria for Mink

A method was developed to follow a lactic acid bacterial strain, Enterococcus faecium Cernelle 68, with respect to adhesion, multiplication, colonization, and persistence in the digestive tract of mink. Also the spread of the strain in the cage was examined. When adding 5 × 109 c.f.u. of a rifampicin resistant mutant per kg feed, high viable counts were registered throughout the digestive tract, apart from the oesophagus. Counts were increasing in the aboral direction, suggesting some multiplication in the intestine. It was possible to detect the strain in the intestinal tract 4 days after discontinuation of administration. Neither culture nor scanning electron microscopy gave evidence to suggest that E. faecium Cernelle 68 adhered to the mucosa. The spread of the E. faecium strain was observed in the environment. Counts of E. coli, lactobacilli, staphylococci, and Clostridia were low, and none of these bacteria were constant findings.     

DVS乳酸菌种菌株传代过程中遗传稳定性分析

目的：对从直投式酸奶发酵剂中分离出的乳酸菌菌株传代过程中的遗传稳定性进行分析。方法：观察传代培养过程中各个菌株在转管不同次数时的形态变化,用RAPD方法分析传代过程中转管不同次数的乳酸菌基因组的变化趋势,并用SDSPAGE对比转管不同次数乳酸菌的蛋白质表达的差异。结果：乳球菌在传代过程中转管不同次数时基因组和蛋白质表达均无变化;乳杆菌1^#在传代过程中转管不同次数时基因组基本无变化,蛋白质表达有变化;乳杆菌2^#在传代过程中转管不同次数时基因组和蛋白质表达均有变化。结论：采用RAPD、SDS-PAGE方法可以有效地对直投式酸奶发酵剂菌株传代过程中的遗传稳定性进行分析。     

Antagonism of Lactic Acid Bacteria against Phytopathogenic Bacteria

A variety of lactic acid bacteria, isolated from plant surfaces and plant-associated products, were found to be antagonistic to test strains of the phytopathogens Xanthomonas campestris, Erwinia carotovora, and Pseudomonas syringae. Effective “in vitro” inhibition was found both on agar plates and in broth cultures. In pot trials, treatment of bean plants with a Lactobacillus plantarum strain before inoculation with P. syringae caused a significant reduction of the disease incidence.     

Surface of Lactic Acid Bacteria: Relationships between Chemical Composition and Physicochemical Properties

The surface chemical composition and physicochemical properties (hydrophobicity and zeta potential) of two lactic acid bacteria, Lactococcus lactis subsp. lactis bv. diacetilactis and Lactobacillus helveticus, have been investigated using cells harvested in exponential or stationary growth phase. The surface composition determined by X-ray photoelectron spectroscopy (XPS) was converted into a molecular composition in terms of proteins, polysaccharides, and hydrocarbonlike compounds. The concentration of the last was always below 15% (wt/wt), which is related to the hydrophilic character revealed by water contact angles of less than 30°. The surfaces of L. lactis cells had a polysaccharide concentration about twice that of proteins. The S-layer of L. helveticus was either interrupted or crossed by polysaccharide-rich compounds; the concentration of the latter was higher in the stationary growth phase than in the exponential growth phase. Further progress was made in the interpretation of XPS data in terms of chemical functions by showing that the oxygen component at 531.2 eV contains a contribution of phosphate in addition to the main contribution of the peptide link. The isoelectric points were around 2 and 3, and the electrophoretic mobilities above pH 5 (ionic strength, 1 mM) were about −3.0 × 10⁻⁸ and −0.6 × 10⁻⁸ m² s⁻¹ V⁻¹ for L. lactis and L. helveticus, respectively. The electrokinetic properties of the latter reveal the influence of carboxyl groups, while the difference between the two strains is related to a difference between N/P surface concentration ratios, reflecting the relative exposure of proteins and phosphate groups at the surface.     

Antioxidant Properties of Lactic Acid Bacteria

Microbiology - Lactic acid bacteria (LAB) are widely used in fermentation processes for the preparation of various foodstuffs, including dairy, meat and vegetable products. In the course of...     

The Screening of Hydrogen Peroxide-Producing Lactic Acid Bacteria and Their Application to Inactivating Psychrotrophic Food-Borne Pathogens

Lactic acid bacteria were isolated from various food samples and evaluated for hydrogen peroxide (H₂O₂) production. Cells suspended in 0.5% (wt/vol) glucose plus 0.5% (wt/vol) lactate (pH 7.0) were incubated for 5 h at 37°C under aeration. Among 193 strains, 27 strains accumulated 201-300 ppm H₂O₂, and 4 strains accumulated more than 301 ppm H₂O₂ in the cell suspensions. Among the 9 high-level H₂O₂-producing strains, 8 strains were identified as Lactococcus lactis subsp. lactis. The cell-free filtrate from Lc. lactis subsp. lactis AI 62, which contained approximately 350 ppm H₂O₂, was evaluated for antimicrobial activity against Enterococcus faecalis, Ent. faecium, enterotoxigenic Escherichia coli, Listeria ivanovii, Staphylococcus aureus, Yersinia enterocolitica, and Aeromonas hydrophila. After 1 h incubation at 30°C in the cell-free filtrate, the initial viable cell counts of the target bacteria (5.53–6.00 log cfu/mL) were reduced by 0.12-5.00 log units, except in the case of enterococci. The sensitivity varied with the bacterial species and pH. The enterococci were resistant to the treatment. Our results show that H₂O₂ accumulated by lactic acid bacteria in a cell suspension is very effective in reducing the viable cell count of food-borne pathogens.Received: 7 October 2002 / Accepted: 4 November 2002     

Lactic Acid Bacteria and Yeasts as Means of Decreasing Wine Acidity

Two hundred monocultures of lactic acid bacteria and 30 associations of yeasts and lactic acid bacteria have been studied. A stable association was developed which was capable of decreasing wine acidity. The association contained two species of bacteria, Leuconostoc oenosand Pediococcus pentosaceus, and the yeast Saccharomyces cerevisiae. The physiology of the microorganisms was studied, and their effects on the chemical composition of wines were determined.     

Lactic Acid Bacteria Convert Human Fibroblasts to Multipotent Cells

The human gastrointestinal tract is colonized by a vast community of symbionts and commensals. Lactic acid bacteria (LAB) form a group of related, low-GC-content, gram-positive bacteria that are considered to offer a number of probiotic benefits to general health. While the role of LAB in gastrointestinal microecology has been the subject of extensive study, little is known about how commensal prokaryotic organisms directly influence eukaryotic cells. Here, we demonstrate the generation of multipotential cells from adult human dermal fibroblast cells by incorporating LAB. LAB-incorporated cell clusters are similar to embryoid bodies derived from embryonic stem cells and can differentiate into endodermal, mesodermal, and ectodermal cells in vivo and in vitro. LAB-incorporated cell clusters express a set of genes associated with multipotency, and microarray analysis indicates a remarkable increase of NANOG, a multipotency marker, and a notable decrease in HOX gene expression in LAB-incorporated cells. During the cell culture, the LAB-incorporated cell clusters stop cell division and start to express early senescence markers without cell death. Thus, LAB-incorporated cell clusters have potentially wide-ranging implications for cell generation, reprogramming, and cell-based therapy.     

猪源乳酸菌产乳酸及其抑菌特性研究

研究了5株(L1、12、L3、L5和L7)分离自仔猪肠道的乳酸菌的产乳酸能力及抑菌特性。结果表明：L5菌株产乳酸的速度最快,培养液中乳酸含量最高,L5菌株培养液pH值的下降速度最快,终末pH值最低,而L1菌株产乳酸的速度最慢,培养液乳酸含量最低。5株乳酸菌对大肠杆菌K88、K99、987P、O141和大肠杆菌E1及金黄色葡萄球菌均有不同程度的抑制作用;排除酸的影响后仍有22％～53％抑菌效果;经热处理后保持有92％以上的抑菌效果;蛋白酶处理后保持85％以上的抑菌效果。     

发菜膜脂及其脂肪酸组成

对野生发菜（Ｎｏｓｔｏｃ ｆｌａｇｅｌｌｉｆｏｒｍｅ Ｂｏｒｎ．ｅｔ Ｆｌａｈ）的膜脂（主要成分为类囊体膜脂）及其脂肪酸组成进行了测定分析。发菜的膜脂由单半乳糖甘油二酯（ＭＧＤＧ）、双半乳糖甘油三酯（ＤＧＤＧ）、磷酯酰甘油（ＰＧ）和硫代异鼠李糖甘油二酯（ＳＱＤＧ）组成,其酯酰基连接有棕榈酸（１６：０）、十六碳烯酸（１６：１）、硬脂酸（１８：０）、油酸（１８：１）、亚油酸（１８：２）和亚麻酸（１８：