Biofloc Technology: Emerging Microbial Biotechnology for the Improvement of Aquaculture Productivity

With the significant increases in the human population, global aquaculture has undergone a great increase during the last decade. The management of optimum conditions for fish production, which are entirely based on the physicochemical and biological qualities of water, plays a vital role in the prompt aquaculture growth. Therefore, focusing on research that highlights the understanding of water quality and breeding systems’ stability is very important. The biofloc technology (BFT) is a system that maximizes aquaculture productivity by using microbial biotechnology to increase the efficacy and utilization of fish feeds, where toxic materials such as nitrogen components are treated and converted to a useful product, like a protein for using as supplementary feeds to the fish and crustaceans. Thus, biofloc is an excellent technology used to develop the aquaculture system under limited or zero water exchange with high fish stocking density, strong aeration, and biota. This review is highlighted on biofloc composition and mechanism of system work, especially the optimization of water quality and treatment of ammonium wastes. In addition, the advantages and disadvantages of the BFT system have been explained. Finally, the importance of contemporary research on biofloc systems as a figure of microbial biotechnology has been emphasized with arguments for developing this system for better production of aquaculture with limited natural resources of water.Key words: biofloc, BFT, aquaculture, microbes, water quality, wastes     

Molecular characterization of Pseudomonas aeruginosa 2NR degrading naphthalene

Three naphthalene-degrading strains were isolated from compost, characterized by morphological and physiological properties and differentiated by 16S rDNA RFLP. During growth on naphthalene, Pseudomonas aeruginosa 2NR produced ortho catechol pathway intermediates and gentisic acid. The ability to accumulate and degrade gentisic acid shows that Ps. aeruginosa 2NR has a different salicylate pathway to that of the intensely studied Ps. putida NCIB 9816. Molecular analysis showed the presence both of genes of the upper naphthalene pathway and genes of the ortho and meta catechol pathways. The insertion of nagH and nagG, coding for salicylate 5-hydroxylase in Pseudomonas sp. U2, was absent in Ps. aeruginosa 2NR, as in Ps. putida NCIMB 9816.     

Retinopathy of prematurity (ROP) and indomethacin therapy in premature infants with paten ductus arterious (PDA)

Recent studies suggested that prostaglandins (PGs) may play a role in the pathogenesis of retinopathy of prematuriry (ROP). To evaluate if PGs inhibitor, indomethacin, would affect the incidence or severity of the ble-blind controlled study of indomethacin for the closure of PDA. Twenty-three were in the control group and 24 in the indometchin group. Indirect ophthalmospic examinations wee performed from about 4 weeks of postnatal age and onward and needed. There was no significant differences between the groups with respect to birth weight, gestational age, postnatal age, Apgar score, and cardiopulmonary status shortly after birth and at the time of study.Six in the control and 2 in the indomethacin group (p=0.58) developed active ROP; one in each group developed cicatricial ROP. It appears that with current doses of therapy, indomethacin does not increase the incidence or severity of ROP.     

Proffered papers 9.30–10.00 Monday 15 September 2003

Both the original Bethesda system and the current UK classifications of cervical cytology have proved robust but each has a major weakness in the area of abnormalities of uncertain significance. Cytologists recognize that sometimes it is simply impossible to differentiate between reactive and dyskaryotic material. For this reason, the Australian version of the Bethesda system introduced a new category of 'high grade inconclusive' with a recommendation for referral to colposcopy. Approximately 60% of such cases are found to have high grade lesions at colposcopy (Schoolland M, Sterrett G, Knowles S et al .). The present UK system even with the proposed changes requires of the pathologist, a decision as to whether such cases are probably high grade (=a report of moderate dyskaryosis) or not (= a report of borderline). This continues to ignore the fact that sometimes you just cannot tell, even on review. We have taken a consecutive series of 50 referral smears, reported as moderate dyskaryosis, where the histological outcome (by loop cone) is known. These cases were rescreened and then reviewed blind by a pathologist with extensive experience of the Australian NH & MRC modified Bethesda system. On review, the material was reclassified along NH & MRC lines. The results were compared with the biopsy findings in order to determine whether the category of 'inconclusive' might be of value in the context of the NHSCSP.     

Antigenic competition and genetic control of the immune response. A hypothesis for intramolecular competition

A study has been made of antigenic competition between the (Phe,Glu) and Pro-Lys regions of three synthetic multichain polypeptides, (Phe,Glu)-Ala-Lys, (Tyr,Glu)-Pro-Lys and (Phe,Glu)-Pro-Lys. Two strains of mice have been compared, C3H/HeJ, potentially high responders to both (Phe,Glu) and Pro-Lys, and DBA/1, high responders to (Phe,Glu), but genetic low responders to Pro-Lys. In C3H/HeJ, both intramolecular competition, within the (Phe,Glu)-Pro-Lys molecule, and intermolecular competition, with mixtures of (Tyr,Glu)-Pro-Lys and (Phe,Glu)-Ala-Lys occur. In general, Pro-Lys is the dominant determinant and suppresses the response to (Phe, Glu). In DBA/1, on the other hand, intramolecular competition is absent, but intermolecular competition is still present. The injection of the polyribonucleotide poly (A)·poly (U) corrects the low response to Pro-Lys in DBA/1, and at the same time restores intramolecular competition. Intramolecular competition is, therefore, related to the level of the antibody response to the dominant antigenic region, Pro-Lys. In contrast, intermolecular competition is independent of the antibody response to Pro-Lys, but is related to the ratio of the antigens (Tyr,Glu)-Pro-Lys and (Phe,Glu)-Ala-Lys in the mixture injected.A model is suggested in which intramolecular competition is a result of competition between specific B cells for limiting antigen. The model relates competition to original antigenic sin and the enhancement and suppression mediated by antibody. Intermolecular competition seems to have a different mechanism and to be a T cell effect. The relevance of these findings to studies on the genetic control of the immune response is discussed.