Inhibition of polygalacturonase and polygalacturonic acid lyase fromErwinia carotovora subsp.carotovora by phenolics in vitro

Summary The phenolic acids benzoic, caffeic, chlorogenic, ferulic, p-coumaric, protocatechuic, salicylic, sinapic, syringic and vanillic together with vanillin, were tested for their ability to inhibit polygalacturonic acid lyase (PL) and polygalacturonase (PG) in culture filtrates ofErwinia carotovora subsp.carotovora. None of the compounds inhibited PL at 200 μg/ml, although syringic and sinapic acids caused a 54% and 43% reduction respectively at 400 μg/ml. PG was strongly inhibited by caffeic acid (57% inhibition at 100 μg/ml) and chlorogenic acid caused slight inhibition. Little if any inhibition of PG was caused by benzoic, ferulic, p-coumaric, protocatechuic, salicylic, sinapic, syringic, and vanillic acids or vanillin. The percentage inhibition of PG by chlorogenic acid was not affected by pH values over the range 4–7.     

Optimal combinations of acute phase proteins for detecting infectious disease in pigs

ABSTRACT: The acute phase protein (APP) response is an early systemic sign of disease, detected as substantial changes in APP serum concentrations and most disease states involving inflammatory reactions give rise to APP responses. To obtain a detailed picture of the general utility of porcine APPs to detect any disease with an inflammatory component seven porcine APPs were analysed in serum sampled at regular intervals in six different experimental challenge groups of pigs, including three bacterial (Actinobacillus pleuropneumoniae, Streptococcus suis, Mycoplasma hyosynoviae), one parasitic (Toxoplasma gondii) and one viral (porcine respiratory and reproductive syndrome virus) infection and one aseptic inflammation. Immunochemical analyses of seven APPs, four positive (C-reactive protein (CRP), haptoglobin (Hp), pig major acute phase protein (pigMAP) and serum amyloid A (SAA)) and three negative (albumin, transthyretin, and apolipoprotein A1 (apoA1)) were performed in the more than 400 serum samples constituting the serum panel. This was followed by advanced statistical treatment of the data using a multi-step procedure which included defining cut-off values and calculating detection probabilities for single APPs and for APP combinations. Combinations of APPs allowed the detection of disease more sensitively than any individual APP and the best three-protein combinations were CRP, apoA1, pigMAP and CRP, apoA1, Hp, respectively, closely followed by the two-protein combinations CRP, pigMAP and apoA1, pigMAP, respectively. For the practical use of such combinations, methodology is described for establishing individual APP threshold values, above which, for any APP in the combination, ongoing infection/inflammation is indicated.     

Stabilizing isopeptide bonds revealed in gram-positive bacterial pilus structure

Many bacterial pathogens have long, slender pili through which they adhere to host cells. The crystal structure of the major pilin subunit from the Gram-positive human pathogen Streptococcus pyogenes at 2.2 angstroms resolution reveals an extended structure comprising two all-beta domains. The molecules associate in columns through the crystal, with each carboxyl terminus adjacent to a conserved lysine of the next molecule. This lysine forms the isopeptide bonds that link the subunits in native pili, validating the relevance of the crystal assembly. Each subunit contains two lysine-asparagine isopeptide bonds generated by an intramolecular reaction, and we find evidence for similar isopeptide bonds in other cell surface proteins of Gram-positive bacteria. The present structure explains the strength and stability of such Gram-positive pili and could facilitate vaccine development.     

Effects of different dietary arachidonic acid : docosahexaenoic acid ratios on phospholipid fatty acid compositions and prostaglandin production in juvenile turbot (Scophthalmus maximus)

Five purified diets containing AA (20:4n-6) at 0.02–0.78% dry weight and DHA (22:6n-3) at 0.93–0.17% dry weight were fed to duplicate groups of juvenile turbot (Scophthalmus maximus) of initial weight 0.87 g for a period of 11 weeks. The dietary DHA:AA ratio ranged from 62 to 0.2. Incorporation of AA into liver phospholipids increased with increasing dietary AA input. Phospholipids from fish fed diets containing 0.02, 0.06 and 0.11% of dry weight as AA generally contained less AA compared to fish fed fish oil while those fed diets containing 0.35 and 0.78% of dry weight as AA had higher AA levels in their phospholipids. The highest levels of AA were found in PI but the greatest percentage increase in AA incorporation was in PE and PC. Brain phospholipid fatty acid compositions were less altered by dietary treatment than those of liver but DHA content of PC and PE in brain was substantially lower in fish fed 0.93% pure DHA compared to those fed fish oil. This suggests that dietary DHA must exceed 1% of dry weight to satisfy the requirements of the developing neural system in juvenile turbot. In both tissues, (20:5n-3) concentration was inversely related to both dietary and tissue PI AA concentration. Similar dietary induced changes in AA, EPA and DHA concentrations occurred in the phospholipids of heart, gill and kidney. PGE₂ and 6-ketoPGF₁ were measured in homogenates of heart, brain, gill and kidney. In general, fish fed the lowest dietary AA levels had reduced levels of prostaglandins in their tissue homogenates while those fed the highest level of AA had increased prostaglandin levels, compared to fish fed fish oil. In brains, the PGE₂ concentration was only significantly increased in fish fed the highest dietary AA.Abbreviations AA arachidonic acid - DHA docosahexaenoic acid - EFA essential fatty acid - EPA eicosapentaenoic acid - HPTLC high performance thin-layer chromatography - HUFA highly unsaturated fatty acid - PC phosphatidylcholine - PE phosphatidylethanolamine - PGE prostaglandin E - PGE prostaglandin E - PI phosphatidylinositol - PS phosphatidylserine - PUFA polyunsaturated fatty acid - TLC thin-layer chromatography     

Effects of putative dietary probiotics from the gut of milkfish (Chanos chanos) on the growth performance and intestinal enzymatic activities of juvenile Nile tilapia (Oreochromis niloticus)

Enzymes synthesized by the gut microbiome are recognized as vital for assisting host metabolism. This study was conducted to screen and identify bacterial isolates with enzyme-producing abilities from the intestine of milkfish Chanos chanos. Overall, 114 isolates were collected, of which 58% showed clear zones indicating various enzyme activities via plate-based assays. Specifically, 65 isolates were amylolytic, 1 isolate was cellulolytic, and 18 isolates exhibited both activities. The two most promising isolates—CC8 and CC27—were further subjected to spectrophotometric enzyme assays to determine their amylase, cellulase and protease activities. Results showed that amylase, cellulase and protease activities (6.00 ± 0.01, 0.52 ± 0.02 and 18.62 ± 0.16 U mg^?1 protein, respectively) were higher in CC8 than in CC27. Using 16S rRNA gene sequencing, the isolates were putatively identified as Vibrio sp. and Bacillus cereus respectively. At a suspension (mL) to feed (g) ratio of 3:25, dietary supplementation of putative probiotics was carried out to evaluate the growth performance, survival and enzymatic activities of juvenile Nile tilapia Oreochromis niloticus. Results revealed that probiotic-supplemented fish exhibited better growth performance—final average body weight, weight gain, specific growth rate and feed conversion ratio—along with increased intestinal enzymatic activities compared with the control (p < 0.05). Survival rates ranged from 80% to 90% and were statistically similar in all treatments (p > 0.05). This study concludes that the application of Vibrio sp. CC8 and Bacillus cereus CC27, supplemented either in monostrain or multistrain preparation, can promote growth and enzymatic activities in juvenile Nile tilapia.     

Isolation of Streptococcus agalactiae and an aquatic birnavirus from doctor fish Garra rufa L

Background

The doctor fish, Garra rufa, has become increasingly popular as a treatment for skin disorders and for pedicures in recent years. Despite this there is very little information available regarding the welfare of these fish and the range of potential pathogens they may carry. In this study, a group of fish suffering from post-transport mortalities were examined and the isolated pathogens identified.

Findings

Group B Streptococcus agalactiae was isolated from kidney swabs of the fish and found to be resistant to a number of antibiotics. In addition to this, a fish virus belonging to the aquabirnavirus group, serogroup C was isolated for the first time in Ireland. However, no clinical signs of disease typical of bacterial or viral infections were observed in any fish examined.

Conclusions

As no clinical signs of disease attributable to either of the pathogens identified were found it was concluded that the mortalities were most likely due to transport related stress exacerbated by the presence of the pathogens. Further work is required to assess the suitability of current transport strategies and to examine the potential risk associated with the transport of live ornamental fish.