Improved nitrogen removal by application of new nitrogen-cycle bacteria

In order to meet increasingly stringentEuropean discharge standards, new applicationsand control strategies for the sustainableremoval of ammonia from wastewater have to beimplemented. In this paper we discuss anitrogen removal system based on the processesof partial nitrification and anoxic ammoniaoxidation (anammox). The anammox process offersgreat opportunities to remove ammonia in fullyautotrophic systems with biomass retention. Noorganic carbon is needed in such nitrogenremoval system, since ammonia is used aselectron donor for nitrite reduction. Thenitrite can be produced from ammonia inoxygen-limited biofilm systems or in continuousprocesses without biomass retention. Forsuccessful implementation of the combinedprocesses, accurate biosensors for measuringammonia and nitrite concentrations, insight inthe complex microbial communities involved, andnew control strategies have to be developed andevaluated.     

Somatic embryogenesis and plantlet regeneration in mango (Mangifera indica L.)

Summary The ‘Carabao’ or ‘Manila Super’ mango (Mangifera indica L.), a virtually neglected fruit before the advent of KNO₃ flower induction in the early 1970s, is now the third leading Philippine export fruit after banana and pineapple. To apply biotechnology for improvement, a reliable embryogenesis and regeneration protocol is required. We have developed a protocol for somatic embryogenesis and plantlet regeneration in mango: eight strains of ‘Carabao’ and two unidentified varieties, PHL 12384 and PHL 12378. Over 40 batches of nucellar explants from immature fruis (0.75–5.0 cm long) were cultured in vitro from April 1999 to April 2000. Two media were used, MMSE. Mango Medium for Somatic Embryo Induction, Proliferation and Germination and MMPR, Mango Medium for Plantlet Regeneration. These are now routinely used. The protocol is reproducible in 14 other varieties of mango. Shifting the base medium from Gamborg's B5 medium to our own formulation. BP medium (Barba and Pate?a's formulation) effectively controlled browning. Browning has limited the successful in vitro culture of many woody species including the mango. Crop Science Society of the Philippines (CSSP) 2001 Best Paper Award, Asian Agriculture Congress, Westin Philippine Plaza, Manila, Philippines, April 24–27, 2001 and Philippine Fruit Association 2000 Best Poster Award, 8th National Symposium. PCARRD, Los Ba?os, Laguna, Philippines, November 14–16, 2000.     

Human Papillomavirus E6E7-Mediated Adenovirus Cell Killing: Selectivity of Mutant Adenovirus Replication in Organotypic Cultures of Human Keratinocytes

Replication-competent adenoviruses are being investigated as potential anticancer agents. Exclusive virus replication in cancer cells has been proposed as a safety trait to be considered in the design of oncolytic adenoviruses. From this perspective, we have investigated several adenovirus mutants for their potential to conditionally replicate and promote the killing of cells expressing human papillomavirus (HPV) E6 and E7 oncoproteins, which are present in a high percentage of anogenital cancers. For this purpose, we have employed an organotypic model of human stratified squamous epithelium derived from primary keratinocytes that have been engineered to express HPV-18 oncoproteins stably. We show that, whereas wild-type adenovirus promotes a widespread cytopathic effect in all infected cells, E1A- and E1A/E1B-deleted adenoviruses cause no deleterious effect regardless of the coexpression of HPV18 E6E7. An adenovirus deleted in the CR2 domain of E1A, necessary for binding to the pRB family of pocket proteins, shows no selectivity of replication as it efficiently kills all normal and E6E7-expressing keratinocytes. Finally, an adenovirus mutant deleted in the CR1 and CR2 domains of E1A exhibits preferential replication and cell killing in HPV E6E7-expressing cultures. We conclude that the organotypic keratinocyte culture represents a distinct model to evaluate adenovirus selectivity and that, based on this model, further modifications of the adenovirus genome are required to restrict adenovirus replication to tumor cells.     

DNA Virus Replication Compartments

Viruses employ a variety of strategies to usurp and control cellular activities through the orchestrated recruitment of macromolecules to specific cytoplasmic or nuclear compartments. Formation of such specialized virus-induced cellular microenvironments, which have been termed viroplasms, virus factories, or virus replication centers, complexes, or compartments, depends on molecular interactions between viral and cellular factors that participate in viral genome expression and replication and are in some cases associated with sites of virion assembly. These virus-induced compartments function not only to recruit and concentrate factors required for essential steps of the viral replication cycle but also to control the cellular mechanisms of antiviral defense. In this review, we summarize characteristic features of viral replication compartments from different virus families and discuss similarities in the viral and cellular activities that are associated with their assembly and the functions they facilitate for viral replication.