Rapid propagation of agave by in vitro tissue culture

A procedure for rapid propagation of Agave (A. cantala Roxb., A. fourcroydes Lem. and A. sisalana Perrine, (Agavaceae) have been developed. The explants were excised from stolon plantlets, sterilized and cultivated on Murashige and Skoog (MS) basal medium containing 2% sucrose, 10% coconut water and 0.8% agar. The addition of following combination of growth substances—0.075 mgl^-1 naphthalenacetic acid (NAA)+0.1 mgl^-1 indolylbutyric acid (IBA)+0.5 mgl^-1 kinetin (KIN) caused an extensive proliferation of multiple shoot primordia. Subcultures of these on the same medium were successful for the multiplication with an index of 3–4 times per 4 weeks subculture period. Shoots were rooted on hormone free MS medium and then transferred into a sand bed for acclimation before field planting.     

Intrinsic factors influence the attachment of fragments of the green alga Caulerpa filiformis

Asexual reproduction via fragmentation is an integral component of the life history of many marine organisms. In south-eastern Australia the green macroalga Caulerpa filiformis (Suhr) Hering is abundant on many rocky shorelines and fragments are very abundant in the water column. We examined some of the factors that may influence the growth and successful reattachment of fragments of C. filiformis that potentially contribute to its success. Field surveys revealed that C. filiformis fragments were of variable morphologies (from small fronds to entire thalli) and sizes (0.1-60 cm in length). All fragments of C. filiformis were viable propagules that survived and grew well in the laboratory. However, some fragments grew more than others, in particular larger sizes (7.5 cm class) of certain morphologies (fragments that consisted only of a single frond). Rhizoids were produced by all fragments, but again, larger fragments produced more rhizoids than smaller fragments. The force required to detach fragments was proportional to the number (but not size) of rhizoids, demonstrating the importance of rhizoids for attachment. The rate of attachment of fragments was also fast, usually within 12 h, but the longer these fragments were attached to a substratum the greater the force required to dislodge them. Interestingly, fragments only produced rhizoids if they were resting on a substratum which may explain the small proportion of fragments with rhizoids in the field (< 5%). Ultimately, the long term success of C. filiformis fragments was low as only 1.6% of fragments attached within 24 h and none of these persisted for longer than 2 days. Nonetheless, the abundance and viability of fragments of C. filiformis available to attach suggest that asexual fragmentation is a successful reproductive strategy in this seaweed.     

Options for In Situ Remediation of Soil Contaminated with a Mixture of Perchlorinated Compounds

Environments contaminated with mixtures of chlorinated hydrocarbons represent a formidable challenge for bioremediation because biodegradation of all components of the mixture must be demonstrated. In this study a soil site contaminated with hexachloro-1,3-butadiene (HCBD), hexachlorobenzene (HCB), and perchloroethene (PCE) was investigated. Environmental parameters (including toxicity) and microbial community composition were characterized. The lack of scientific literature on HCBD biodegradation led to attempts to develop HCBD-respiring enrichment cultures and to test the hypothesis that known PCE-degrading cultures could dechlorinate HCBD. No HCBD dechlorination was observed. An alternative approach, using electron shuttles to degrade the mixture of chlorinated hydrocarbons, was compared with the activity of zero-valent iron. The authors conclude that electron shuttles offer promise for the in situ treatment of mixtures of chlorinated hydrocarbons.     

Characterization of mouse and human B7-H3 genes

T cell activation and immune function are regulated by costimulatory molecules of the B7 superfamily. Human B7-H3 is a recent addition to this family and has been shown to mediate T cell proliferation and IFN-gamma production. In this work we describe the identification of the mouse B7-H3 homolog, which is ubiquitously expressed in a variety of tissues. Activated CD4 and CD8 T cells express a putative receptor that can be recognized by soluble mouse B7-H3-Ig molecules. While the mouse B7-H3 gene was found to contain a single copy, we discovered a novel isoform of human B7-H3 (named as B7-H3b hereafter) with four Ig-like domains that results from gene duplication and differential splicing. B7-H3b is the major isoform expressed in several tissues. This structural information suggests a genetic variation of the B7-H3 gene in mammalian species.