Lipid A derived from Pseudomonas aeruginosa PAO1 contains a biphosphorylated 1-6-linked glucosamine disaccharide backbone. The reducing glucosamine has an unsubstituted glycosidically linked phosphate at C-1. The nonreducing glucosamine has an ester-bound phosphate at C-4' which is nonstoichiometrically substituted with 4-amino-4-deoxyarabinose. Induction of 4-amino-4-deoxyarabinose was dependent on cultural conditions. No pyrophosphate groups were detected. Acyloxyacyl diesters are formed by esterification of the amide-bound 3-hydroxydodecanoic acid with dodecanoic acid and 2-hydroxydodecanoic acids in an approximate molar ratio of 2:1. Dodecanoic and 3-hydroxydecanoic acids are esterified to positions C-3 and C-3' in the sugar backbone. All hydroxyl groups of the glucosamine disaccharide except C-4 and C-6' are substituted. Lipopolysaccharide chemical analyses measured glucose, rhamnose, heptose, galactosamine, alanine, phosphate, and glucosamine. The proposed lipid A structure differs from previous models. There are significant differences in acyloxyacyl diesters, and the proposed model includes an aminopentose substituent.Lipopolysaccharides (LPS) are major components of the gram-negative bacterial outer membrane and are essential for the assembly, organization, and functioning of this vital structure. LPS contributes to the pathophysiology of the notorious opportunistic pathogen Pseudomonas aeruginosa by functioning as a virulence factor and acting in consort with other outer membrane constituents to form a permeability barrier against antimicrobial agents (14).P. aeruginosa LPS is compositionally similar to enterobacterial LPS (12). These structural similarities include a biphosphorylated D-glucosamine disaccharide lipid A backbone, an oligosaccharide core, and serologically diverse 0 chains. However, P. aeruginosa LPS differs from enterobacterial LPS by having a large number of phosphate residues, by the presence of L-alanine in the core, and by the occurrence of unusual sugars and amino compounds in the 0 chain (15,20).Enterobacterial lipid A's have a number of features that serve to distinguish them from their pseudomonal counterparts. One such structure is 4-amino-4-deoxyarabinose (4-AraN), which is found in some but not all enteric lipid A's. The physiological function of 4-AraN is unresolved, although it has been suggested by Vaara et al. to play a role in resistance against selected antibiotics by substituting onto lipid A phosphate groups (28,29). In this capacity the cationic 4-AraN could facilitate resistance by either repulsing positively charged antimicrobial agents such as polymyxin B or by occupying their LPS attachment sites. Vaara et al. also proposed that resistance to polymyxin B is proportional to the number of lipid A phosphate groups substituted with 4-AraN. 4-AraN substitution in LPS has been previously reported in selected members of the family Enterobacteriaceae, in Chromobacterium violaceum, and in phototrophic bacteria (8,22,26,27 In this study we report the isolation and partial ...

Antimicrobial peptides (AMPs) are the key components of the innate immune system and perform the various biological function which offers immunocompetence and homeostasis to the living organisms. Owing to their multidimensional properties, they can find an important role in therapeutics for the treatment of emerging diseases in fishes. Several AMPs are reported in fishes, including defensins, cathelicidins, hepcidins, histone‐derived peptides and piscidins having board antimicrobial spectrum. Various factors are necessary for the induction of AMPs expression like pathogen‐associated molecular patterns and damage‐associated molecular pattern. Moreover, with beneficial effects, AMPs are coupled with rare concerns which should be considered before bringing them under the label of ‘harmless alternative to antibiotics’.

No abstract

No abstract

In fish, as in higher animals, the normal ontogenesis of the gonads is the basis for successful reproduction. Gonadal differentiation and development depend on the genetic cascade that programmes the events. Eventually, gonads become the sites for the maturation of gametes, which are originally derived from the primordial germ cells (PGCs) and form the cellular basis of reproduction. In fish hormones of the hypothalamic-pituitary-gonadal (HPG) axis regulate reproduction and fertility by promoting or inhibiting the production of gonadal sex steroids and their function. Gonadal sex steroids not only guide proper gonadal development and function but also play a key role in the activation and regulation of the HPG axis through two feedback control systems. In this review, we discuss the general outline and expression pattern of the major genes involved in testicular development and gonadal steroidogenesis in fish. The review attempts, for the first time, to collect and discuss recent information regarding the regulation of sex differentiation and steroidogenic genes during the stages of testicular development and in response to different external factors. Furthermore, clear insights into the important genes and their regulation involved in the HPG axis and spermatogenesis are presented briefly. This review can serve as a guide for fish breeders on the substances that have a positive impact on reproduction in males.

No abstract

No abstract

No abstract