In the past few decades, genome-based approaches have contributed significantly to vaccine development. Our aim was to identify the most conserved and immunogenic antigens of Streptococcus pneumoniae, which can be potential vaccine candidates in the future. BLASTn was done to identify the most conserved antigens. PSORTb 3.0.2 was run to predict the subcellular localization of the proteins. B cell epitope prediction was done for the immunogenicity testing. Finally, BLASTp was done for verifying the extent of similarity to human proteome to exclude the possibility of autoimmunity. Proteins failing to comply with the set parameters were filtered at each step. Based on the above criteria, out of the initial 22 pneumococcal proteins selected for screening, pavB and pullulanase were the most promising candidate proteins.
Talukdar S., Ringø E., Ghosh K. 2016. Extracellular tannase-producing bacteria detected in the digestive tracts of freshwater fi shes (Actinopterygii: Cyprinidae and Cichlidae). Acta Ichthyol. Piscat. 46 (3): 201-210.Background. Although, presence of tannase-producing and/or tannin tolerant gut bacteria has been documented in ruminants and non-ruminant herbivores, the topic is rarely addressed in fi sh. The present study aimed at enumeration of autochthonous tannase-producing bacteria in the gut of freshwater teleosts. Gastrointestinal (GI) tracts of the fi sh studied were divided into proximal (PI) and distal (DI) parts, homogenized and plated onto Tryptone Soya Agar (TSA) plates. The pure colonies were spotted on selective tannic acid (TA) agar plates to determine the tannase-producing bacteria. Extracellular tannase-producing capacity of the isolates was determined through qualitative and quantitative assay using TA media plates or broth, respectively at three different pH levels (5.5, 7.0, and 8.5). Further, 16S rRNA gene fragments of the promising tannase-producing bacteria were sequenced, aligned, analysed, identifi ed, and deposited to the GenBank. Results. Totally 685 strains were isolated on TSA plates, of which 116 strains (37 from PI and 79 from DI) grow on TA media and were defi ned as tannase-producers. The highest percentage of tannase-producing strains was noticed in the DI regions of grass carp, Ctenopharyngodon idella (38.98%), and tilapia, Oreochromis niloticus (37.74%). The lowest frequency of tannase-producing bacteria was revealed in PI region of catla, Catla catla (2.12%). The intestine of Indian major carps was relatively poorly colonized by tannase-producing bacteria compared to that of exotic carps. Evaluation of tannase-producing capacity revealed that the majority of the isolates exhibited maximum extracellular tannase production at pH 7.0. Quantitative evaluation, showed highest tannase activity by strain HMT1 (0.28 ± 0.001 U) isolated from silver carp, Hypophthalmichthys molitrix, followed by strains ONH2Ph (0.19 ± 0.005) and ONH13B (0.17 ± 0.009 U) isolated from tilapia. Analyses of the 16S rRNA partial gene sequences revealed that strains ONH2Ph and ONH13B showed high similarity to Bacillus subtilis (KP765736) and Brevibacillus agri (KP765734), respectively. Whereas, strain HMT1 was most closely related to Klebsiella variicola (KP765735). Conclusions. The study revealed existence of tannase-producing bacterial symbionts within fi sh GI tracts. Tannindegrading bacteria detected in the presently reported study might aid in overcoming the anti-nutritional effects of dietary tannins within fi sh gut.
This study was intended to evaluate tannin mediated inhibition of digestive proteases in two different size groups (fingerlings, F, 4.5 ± 0.7 cm; advanced fingerlings, AF, 18.2 ± 1.6 cm) of rohu, Labeo rohita. Graded levels (50, 100, 150 and 200 nM) of tannin (Gallotannin, 99% purity) were added to the enzyme extracts (30°C, 1 hr) prior to determination of enzyme activities. Changes in the activity of trypsin, chymotrypsin and total protease in relation to the control sets were determined through biochemical assay of enzymes and SDS-PAGE zymography. The study revealed that tannin significantly inhibited trypsin, chymotrypsin and total protease activities in a dose dependent manner as evident from the regression equations.The degree of the inhibition appeared to be significantly higher for the F in contrast to the AF (F 5,66 = 282.311; p < 0.0001). Trypsin activities were reduced by 8.04 ± 0.19% to 52.68 ± 0.72% and 5.61 ± 0.22% to 39.46 ± 0.19% in F and AF, respectively. The reduction in Chymotrypsin activities ranged between 16.11 ± 0.03% to 38.02 ± 0.27% in F and 6.31 ± 0.07% to 22.80 ± 0.32% in AF.Total protease activities were reduced by 10.9 ± 0.07% to 49.60 ± 0.32% in L. rohita F, whereas, it ranged between 5.19 ± 0.06% to 32.60 ± 0.13% in AF. On a comparative scale, the difference in tannin induced inhibition in F and AF were more prominent for trypsin and chymotrypsin than total protease. Further, nine protease activity bands (15.9-69 kD) with different electromobility were noticed in both the size groups. Subsequent densitometry analysis revealed that the average densities of the protease activity bands were gradually decreased with increasing level of tannin exposure (50-200 nM). The study might indicate adaptive tolerance to tannin in larger size groups and emphasizes the need for removal of tannin in the plant feedstuffs, especially for feeding the fingerlings of L. rohita. K E Y W O R D S
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