首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
Thirty samples of Italian durum wheat semolina and whole durum wheat semolina, generally used for the production of Southern Italy's traditional breads, were subjected to microbiological analysis in order to explore their lactic acid bacteria (LAB) diversity and to find strains with antifungal activity. A total of 125 presumptive LAB isolates (Gram-positive and catalase-negative) were characterized by repetitive extragenic palindromic-PCR (REP-PCR) and sequence analysis of the 16S rRNA gene, leading to the identification of the following species: Weissella confusa, Weissella cibaria, Leuconostoc citreum, Leuconostoc mesenteroides, Lactococcus lactis, Lactobacillus rossiae and Lactobacillus plantarum. The REP-PCR results delineated 17 different patterns whose cluster analysis clearly differentiated W. cibaria from W. confusa isolates. Seventeen strains, each characterized by a different REP-PCR pattern, were screened for their antifungal properties. They were grown in a flour-based medium, comparable to a real food system, and the resulting fermentation products (FPs) were tested against fungal species generally contaminating bakery products, Aspergillus niger, Penicillium roqueforti and Endomyces fibuliger. The results of the study indicated a strong inhibitory activity – comparable to that obtained with the common preservative calcium propionate (0.3% w/v) – of ten LAB strains against the most widespread contaminant of bakery products, P. roqueforti. The screening also highlighted the unexplored antifungal activity of L. citreum, L. rossiae and W. cibaria (1 strain), which inhibited all fungal strains to the same or a higher extent compared with calcium propionate. The fermentation products of these three strains were characterized by low pH values, and a high content of lactic and acetic acids.  相似文献   

2.
Microbial community structure and population dynamics during spontaneous bamboo shoot fermentation for production of ‘soidon’ (indigenous fermented food) in North‐east India were studied using cultivation‐dependent and cultivation‐independent molecular approaches. Cultivation‐dependent analyses (PCR‐amplified ribosomal DNA restriction analysis and rRNA gene sequencing) and cultivation‐independent analyses (PCR‐DGGE, qPCR and Illumina amplicon sequencing) were conducted on the time series samples collected from three independent indigenous soidon fermentation batches. The current findings revealed three‐phase succession of autochthonous lactic acid bacteria to attain a stable ecosystem within 7 days natural fermentation of bamboo shoots. Weissella spp. (Weissella cibaria, uncultured Weissella ghanensis) and Lactococcus lactis subsp. cremoris predominated the early phase (1–2 days) which was joined by Leuconostoc citreum during the mid‐phase (3 days), while Lactobacillus brevis and Lactobacillus plantarum emerged and became dominant in the late phase (5–7 days) with concurrent disappearance of W. cibaria and L. lactis subsp. cremoris. Lactococcus lactis subsp. lactis and uncultured Lactobacillus acetotolerans were predominantly present throughout the fermentation with no visible dynamics. The above identified dominant bacterial species along with their dynamics can be effectively utilized for designing a starter culture for industrialization of soidon production. Our results showed that a more realistic view on the microbial ecology of soidon fermentation could be obtained by cultivation‐dependent studies complemented with cultivation‐independent molecular approaches. Moreover, the critical issues to be considered for reducing methodological biases while studying the microbial ecology of traditional food fermentation were also highlighted with this soidon fermentation model.  相似文献   

3.
One hundred and fifty-six strains isolated from corn (Zea mays L.), forage paddy rice (Oryza sativa L.), sorghum (Sorghum bicolor L.) and alfalfa (Medicago sativa L.) silages prepared on dairy farms were screened, of which 110 isolates were considered to be lactic acid bacteria (LAB) according to their Gram-positive and catalase-negative characteristics and, mainly, the lactic acid metabolic products. These isolates were divided into eight groups (A-H) based on the following properties: morphological and biochemical characteristics, γ-aminobutyric acid production capacity, and 16S rRNA gene sequences. They were identified as Weissella cibaria (36.4%), Weissella confusa (9.1%), Leuconostoc citreum (5.3%), Leuconostoc lactis (4.9%), Leuconostoc pseudomesenteroides (8.0%), Lactococcus lactis subsp. lactis (4.5%), Lactobacillus paraplantarum (4.5%) and Lactobacillus plantarum (27.3%). W. cibaria and W. confusa were mainly present in corn silages, and L. plantarum was dominant on sorghum and forage paddy rice silages, while L. pseudomesenteroides, L. plantarum and L. paraplantarum were the dominant species in alfalfa silage. The corn, sorghum and forage paddy rice silages were well preserved with lower pH values and ammonia-N concentrations, but had higher lactic acid content, while the alfalfa silage had relatively poor quality with higher pH values and ammonia-N concentrations, and lower lactic acid content. The present study confirmed the diversity of LAB species inhabiting silages. It showed that the differing natural populations of LAB on these silages might influence fermentation quality. These results will enable future research on the relationship between LAB species and silage fermentation quality, and will enhance the screening of appropriate inoculants aimed at improving such quality.  相似文献   

4.
Sturgeons are one of the most important and valuable species in the Caspian Sea. This investigation (2000–2002) was aimed at determining the feeding habits and the main and secondary prey organisms consumed by the Persian sturgeon (Acipenser persicus Borodin, 1897) living at depths less than 10 m in the Caspian Sea (Guilan Province). The food spectrum of immature A. persicus was comprised of benthic invertebrates of seven genera and fishes of three genera. The main prey items of immature A. persicus were polychaete worms and the secondary prey were crustaceans. The study of stomach contents showed that polychaetes were the most important component of the diet of immature A. persicus of the length class up to 25 cm.  相似文献   

5.
Molecular species identification methods are an important component of CITES monitoring programs for trade in sturgeon and caviar. To date, obtaining molecular evidence for distinguishing caviar from four closely related Eurasian sturgeon species Acipenser baerii (Siberian sturgeon), A. gueldenstaedtii (osetra), A. persicus (Persian sturgeon), A. naccarii (Italian sturgeon) remains problematic. Using approximately 2.3 kb of mtDNA sequence data (cytochrome b, NADH5, control region), we find this to be attributable to the polyphyletic nature of these mitochondrial DNA markers in the Russian sturgeon, A. gueldenstaedtii. Two mitochondrial lineages are present within this species: one is phylogenetically affiliated with A. persicus and A. naccarii, while the other clusters with A. baerii. These findings have a direct impact on molecular testing of commercial caviar and demonstrate the necessity of using large sample sizes when constructing forensic databases. Furthermore, the results affect current taxonomic designations for these species as well as hypotheses concerning their evolutionary origins.  相似文献   

6.
The anaethetic effects of 2‐phenoxyethanol (2‐PE) on possible primary (cortisol level) and secondary (hematological indices and glucose level) stress responses were studied in Persian sturgeon (Acipenser persicus). Fish were first exposed to 0.1, 0.3, 0.5, 0.7, 0.9 and 1.1 ml L?1 2‐PE, and the time to induction (deep anaethesia) and recovery were measured. At a concentration of 0.1 ml L?1, 2‐PE failed to induce deep anaethesia in fish, whereas at concentrations of 0.7, 0.9 and 1.1 ml L?1 all fish were anaethetized within 3 min of exposure. For assessing possible stress effects caused by effective concentrations of 2‐PE, the hematological indices, serum cortisol and glucose were determined in the deeply anaethetized fish as stress indicators. The 2‐PE exposure resulted in significant increases in red blood cell (RBC) values at 0.3 and 0.5 ml L?1; parallel increases in hemoglobin values were also observed at these concentrations (P < 0.01). Moreover, a lower concentration of 2‐PE (0.3 ml L?1) caused a significant increase in hematocrit values (P < 0.05). Among the hematological indices, mean corpuscular volume (MCV) values decreased at 0.5 ml L?1 when compared with the control and other groups (P < 0.05). Serum cortisol level was elevated at 0.3, 0.5 and 0.7 concentrations of 2‐PE (P < 0.01). The glucose level followed a trend similar to that observed for cortisol. The outcome of these experiments shows that 2‐PE at a concentration of 0.9 ml L?1 is a suitable anaesthetic for Persian sturgeon. This study demonstrates that rapid induction of deep anaethesia with a relatively high concentration of 2‐PE (0.9 and 1.1 ml L?1) was associated with the lowest effects on signs of physiological stress in Persian sturgeon.  相似文献   

7.
Aims: The gram‐positive bacterial genus Lactococcus has been taxonomically classified into seven species (Lactococcus lactis, Lactococcus garvieae, Lactococcus piscium, Lactococcus plantarum, Lactococcus raffinolactis, Lactococcus chungangensis and Lactococcus fujiensis). This study aimed to develop a novel multiplex polymerase chain reaction (PCR) primer set for the identification of the seven lactococcal species, as well as to differentiate the two industrially important dairy subspecies, L. lactis subsp. lactis and L. lactis subsp. cremoris. Methods and Results: A multiplex PCR primer set was designed based on the nucleotide sequences of the 16S rRNA gene of the seven lactococcal species. The specificity of the established one‐step multiplex PCR scheme was verified using more than 200 bacterial strains, in which a complete sequence match was confirmed by partial sequencing of their 16S rRNA gene. Conclusions: The one‐step multiplex PCR enables the identification and speciation of bacterial strains belonging to the genus Lactococcus and the differentiation of strains of L. lactis subsp. lactis and L. lactis subsp. cremoris. Significance and Impact of the Study: This work provides an efficient method for identification of lactococcal strains of industrial importance.  相似文献   

8.
The morphological characteristics of the pectoral fin spine were compared in three species of sturgeon, the Persian sturgeon (Acipenser persicus), the Russian sturgeon (Acipenser gueldenstaedtii), and the Starry sturgeon (Acipenser stellatus), all sampled from the Caspian Sea. On the basis of morphological characters of the pectoral fin spine, 62.2% of the individuals were correctly classified into separate groups. The cluster analysis also divided the three species into two major subgroups. Acipenser persicus and A. gueldenstaedtii were grouped together, suggesting a similar evolutionary basis. Significant morphological heterogeneity in pectoral fin spine characteristics was observed among the three sturgeon species. Principal component analysis identified the largest differences were in the pectoral fin spine size and the angle between distal pectoral fin spine and the horizontal line (A°). The first and second principal components (PC1 and PC2) of all observations accounted for 64.19% and 14.33% of the total variation, respectively. The combination of all analyses showed the relevance of applying pectoral fin spine shape for interspecific distinction of the three species of sturgeons.  相似文献   

9.
The effects of 14 days exposure to sublethal concentrations of endosulfan (10 and 40 μg L?1) were investigated in mRNA‐ P450 1A expression, antioxidant enzymes (SOD and CAT) activity and histopathological alterations of Persian sturgeon (Acipenser persicus) fingerlings with weights of 3–5 g. The results illustrated that the relative mRNA‐ P450 1A expression level significantly increased (P < 0.05) compared to the control group. Highest significant increase (P < 0.05) was observed on the first day, then decreased towards day 14 of exposure. The SOD and CAT activity showed a significant increase in fish exposed to different concentrations up to day 7, then activity decreased on day 14 in fish of all treated groups. Although signs of tissue lesions were observed on day 4, they increased from day 7 and reached the highest level on day 14. The magnitude of all changed studied parameters (gene expression, enzymes and histopathological) follows a concentration‐dependent manner.  相似文献   

10.
Legally certified sturgeon fisheries require population protection and conservation methods, including DNA tests to identify the source of valuable sturgeon roe. However, the available genetic data are insufficient to distinguish between different sturgeon populations, and are even unable to distinguish between some species. We performed high‐throughput single‐nucleotide polymorphism (SNP)‐genotyping analysis on different populations of Russian (Acipenser gueldenstaedtii), Persian (A. persicus), and Siberian (A. baerii) sturgeon species from the Caspian Sea region (Volga and Ural Rivers), the Azov Sea, and two Siberian rivers. We found that Russian sturgeons from the Volga and Ural Rivers were essentially indistinguishable, but they differed from Russian sturgeons in the Azov Sea, and from Persian and Siberian sturgeons. We identified eight SNPs that were sufficient to distinguish these sturgeon populations with 80% confidence, and allowed the development of markers to distinguish sturgeon species. Finally, on the basis of our SNP data, we propose that the A. baerii‐like mitochondrial DNA found in some Russian sturgeons from the Caspian Sea arose via an introgression event during the Pleistocene glaciation.  相似文献   

11.
We carried out the comparative study of the substrate and inhibitory specificity of liver monoamine oxidases (MAO) of the giant sturgeon Huso huso, the starred sturgeon Acipenser stellatus, the Persian sturgeon Acipenser persicus, and the Russian sturgeon Acipenser gueldenstaedtii. Results of the substrate-inhibitor analysis with use of inhibitors chlorgilin and deprenil, as well as five specific substrates indicate homogeneity of these enzymes. All studied MAO have the several orders higher sensitivity to chlorgilin than to deprenil, with essential interspecies differences being observed. There are determined kinetic parameters of enzymatic deamination (K M and V) of tyramine, serotonin, noradrenalin, benzylamine, β-phenylethylamine, and N-methylhistamine. All studied enzymes have been established to have the higher activity toward serotonin and noradrenalin-substrates of the MAO A form as compared with benzylamine, β-phenylethylamine, and N-methylhistamine-substrate of the mammalian MAO B form, the maximal activity being characteristic of the giant sturgeon.  相似文献   

12.
Morphological and molecular genetic analyses of the Russian sturgeon sensu Berg (1934) were accomplished using the sample of individuals collected in the southern part of the Caspian Sea. The distribution of specimens in the space of principal components calculated using 28 morphometric characters demonstrates the absence of separate clusters. Frequency distributions of six studied meristic characters are unimodal and do not demonstrate the existence of morphologically distinguishable forms within the analyzed sample. The results of molecular genetic study, based on the cytochrome b polymorphism analysis of the same sample of fish, demonstrate its homogeneity. The joined results of morphological and molecular genetic analyses of the Russian sturgeon sensu Berg (1934) do not support the validity of the Persian sturgeon as a separate species Acipenser persicus. The text was submitted by the authors in English  相似文献   

13.
In order to evaluate the protein and energy requirement of Persian sturgeon (Acipenser persicus) sub‐yearlings, eight experimental diets containing two protein levels (40% and 45%) and four lipid levels (10%, 15%, 20% and 25%) were tested. Sturgeons (W0 = 136.8 g) were fed the experimental diets to satiation four times daily for 150 days, resulting in a final mean weight of 375.8 g. Growth was significantly affected by lipid content of the diets. At 40% protein level, weight gain and specific growth rate (% per day) were significantly improved (P < 0.05) by increasing the dietary lipid (energy) content. Protein efficiency ratio (PER) was significantly affected by different dietary treatments for each dietary protein level tested, reaching a mean value of 3.58 in fish fed high lipid diets and a PER of 2.77 in low lipid diets. Results obtained in the present study suggest that the optimum dietary protein content for Persian sturgeon is 40%, with an estimated optimum protein‐to‐energy ratio of 18–20 mg kJ−1.  相似文献   

14.
A total of 140 lactic acid bacteria (LAB) strains were isolated from corn, alfalfa, clover, sainfoin, and Indian goosegrass in the Tibetan Plateau. According to phenotypic and chemotaxonomic characteristics, 16S rDNA sequence, and recA gene PCR amplification, these LAB isolates were identified as belonging to five genera and nine species. Corn contained more LAB species than other forage crops. Leuconostoc pseudomesenteroides, Lactococcus lactis subsp. lactis, Lactobacillus brevis, and Weissella paramesenteroides were dominant members of the LAB population on alfalfa, clover, sainfoin, and Indian goosegrass, respectively. The comprehensive 16S rDNA and recA-based approach effectively described the LAB community structure of the relatively abundant LAB species distributed on different forage crops. This is the first report describing the diversity and natural populations of LAB associated with Tibetan forage crops, and most isolates grow well at or below 10°C. The results will be valuable for the future design of appropriate inoculants for silage fermentation in this very cold area.  相似文献   

15.
It was established that, as in many other representatives of Teleostei, there is a pheromonal regulation of reproductive behavior in Acipenseridae. The postovulatory releasing sex pheromone in Russian sturgeon Acipenser gueldenstaedtii, Persian sturgeon A. persicus, and starred sturgeon A. stellatus is in the ovarian fluid of females, whose odor has an interspecific efficiency and causes manifestation of typical spawning behavior (increase in locomotor activity, attraction to the site of solution presentation, circular swimming, and slightly convulsive movements) in mature males of its own and closely related species. A relationship was found between the ability of males injected with suspension of acetonized hypotheses of acipenserids to respond to odor of ovarian fluid and by both quality and quantity of sperm obtained from them. Data obtained extend our concepts of the role of chemical reception in biology of acipenserids and the range of their chemocommunications.  相似文献   

16.

Background  

Lactococcus garvieae is a bacterial pathogen that affects different animal species in addition to humans. Despite the widespread distribution and emerging clinical significance of L. garvieae in both veterinary and human medicine, there is almost a complete lack of knowledge about the genetic content of this microorganism. In the present study, the genomic content of L. garvieae CECT 4531 was analysed using bioinformatics tools and microarray-based comparative genomic hybridization (CGH) experiments. Lactococcus lactis subsp. lactis IL1403 and Streptococcus pneumoniae TIGR4 were used as reference microorganisms.  相似文献   

17.
Aims: Kava beverages are highly perishable even under refrigerated conditions. This study aimed to investigate the bacterial community dynamics in kava beverages during refrigeration. Methods and Results: Four freshly made kava beverages were obtained from kava bars and stored at 4°C. On days 0, 3 and 6, the aerobic plate count (APC), lactic acid bacteria (LAB) count and yeast and mould count (YMC) of the samples were determined. Meanwhile, bacterial DNA was extracted from each sample and subjected to the polymerase chain reaction‐denaturing gradient gel electrophoresis (PCR‐DGGE). Moreover, species‐specific PCR assays were employed to identify predominant Pseudomonas spp. involved in kava spoilage. Over the storage period, the APC, LAB count and YMC of the four kava beverages all increased, whereas their pH values decreased. The DGGE profile revealed diverse bacterial populations in the samples. LAB, such as Weissella soli, Lactobacillus spp. and Lactococcus lactis, were found in the kava beverages. Species‐specific PCR assays detected Pseudomonas putida and Pseudomonas fluorescens in the samples; Ps. fluorescens became dominant during refrigeration. Conclusions: LAB and Pseudomonas may play a significant role in the spoilage of kava beverages. Significance and Impact of the Study: This study provides important information that may be used to extend the shelf life of kava beverages.  相似文献   

18.
The objectives of this study were to compare the physicochemical properties of coelomic fluid (CF) in three sturgeon species, sterlet sturgeon Acipenser ruthenus (age 5–8 years), Siberian sturgeon Acipenser baerii (age 15–20 years), and Russian sturgeon Acipenser gueldenstaedtii (age 13–18 years). For the study, CF was collected by plastic pipette from the eggs of mature female sterlet sturgeon (N = 10), Siberian sturgeon (N = 7) and Russian sturgeon (N = 4); osmolality, pH, ionic composition (Na+, K+, Ca2+, Mg2+, Cl?), glucose, cholesterol and total protein of the CF were then analyzed. Mean concentration of K+ (4.4–6.11 mmol/L), Cl? (89.8–98.0 mmol/L), Ca2+ (0.87–0.96 mmol/L), Mg2+ (0.57–0.67 mmol/L), cholesterol (0.13–0.16 mmol/L), total protein (2.41–3.57 g/L), pH (7.92–7.98), and osmolality (190–213 mOsm/kg) of CF were not significantly different among these three species. However, the mean concentration of Na+ was significantly lower in sterlet sturgeon (104.6 ± 7.7 mmol/L; p < .05) than in the Siberian (126.4 ± 6.2) and Russian (123.0 ± 5.9) sturgeon. For these three species, Na+, K+, Cl?, and Mg2+ were the dominating ions; several significant correlations were observed among these ions and other physiochemical properties of CF. This is the first report on the ionic and biochemical composition of the CF of sterlet, Siberian and Russian sturgeon, which can be used as a reference point for further development of artificial media for the short‐term storage of unfertilized sturgeon eggs as well as for the standardization of the fertilization protocol for these species in controlled reproduction.  相似文献   

19.
After enrichment of Odontesthes platensis intestinal contents, 53 lactic acid bacteria (LAB) were isolated. From the four isolates that showed inhibitory activity against Lactococcus garvieae 03/8460, strain TW34 was selected because it exerted the strongest inhibition. It also inhibited other Gram-positive bacteria, but not Gram-negative fish pathogens. Phenotypic and 16S rDNA phylogenetic analyses showed that TW34 belongs to Lactococcus lactis. In addition, TW34 showed to be sensitive to different antibiotics. The production of the inhibitory agent against L. garvieae was growth associated, and it was significantly influenced by the incubation temperature. The optimal temperature for the antimicrobial production was as low as 15°C. Both acidification and hydrogen peroxide production were ruled out as the source of inhibition. In contrast, the antimicrobial activity was completely lost by treatment with proteolytic enzymes, which confirmed that the inhibitory substance was a bacteriocin. The bacteriocin was highly thermostable (121°C for 15 min) and active between pH 3 and 11. It remained stable for up to 2 months when stored at 4°C and up to 6 months at −20°C. Our results suggest that the strain L. lactis TW34 could provide an alternative for lactococcosis control and therefore be considered for future challenge experiments with fish.  相似文献   

20.
Summary We investigated the effects of lactic acid bacterial (LAB) cells in rats using fluorescence in situ hybridization (FISH) targeting 16S rRNA to identify the cecal microbial community. We designed a novel species-specific 16S rDNA probe to detect Lactobacillus rhamnosus (Lrham454). Subtractive technique using the LAC722 probe (Sakai et al. 2004 Journal of Bioscience and Bioengineering 98, 48) under different hybridization stringency (LAC722(L-H)) was applied to identify Lactococcus lactis. We also applied Lplan447 and LAC722(L) to detect Lactobacillus plantarum and a wide range of LAB (total LAB), respectively. We optimized the hybridization and washing conditions and then quantified L. rhamnosus, L. plantarum, and L. lactis cells in rat cecal contents. We monitored increases in individual bacterial populations and in total LAB caused by the administration of the corresponding LAB cells. Growth, food efficiency and internal disorders did not significantly differ among the rats administered with LABs. Rats administered with polydextrose (POL) developed diarrhea, which decreased the total numbers of cecal bacteria, whereas the simultaneous administration of POL and L. rhamnosus KY-3 eased this symptom, and recovered the numbers of total LAB and of L. rhamnosus.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号