Cyanobacteria-bryophyte symbioses.

Cyanobacteria are a large group of photosynthetic prokaryotes of enormous environmental importance, being responsible for a large proportion of global CO(2) and N(2) fixation. They form symbiotic associations with a wide range of eukaryotic hosts including plants, fungi, sponges, and protists. The cyanobacterial symbionts are often filamentous and fix N(2) in specialized cells known as heterocysts, enabling them to provide the host with fixed nitrogen and, in the case of non-photosynthetic hosts, with fixed carbon.

Mutation at different sites in the Nostoc punctiforme cyaC gene, encoding the multiple-domain enzyme adenylate cyclase, results in different levels of infection of the host plant Blasia pusilla.

The filamentous cyanobacterium Nostoc punctiforme forms symbioses with plants. Disruption of the catalytic domain of the N. punctiforme adenylate cyclase (CyaC) significantly increased symbiotic competence, whereas reduced infectivity was observed in a mutant with a disruption close to the N terminus of CyaC.

Molecular analysis of genes in Nostoc punctiforme involved in pilus biogenesis and plant infection.

Hormogonia are the infective agents in many cyanobacterium-plant symbioses. Pilus-like appendages are expressed on the hormogonium surface, and mutations in pil-like genes altered surface piliation and reduced symbiotic competency. This is the first molecular evidence that pilus biogenesis in a filamentous cyanobacterium requires a type IV pilus system.

Fate of genetically modified maize DNA in the oral cavity and rumen of sheep.

The polymerase chain reaction (PCR) technique was used to investigate the fate of a transgene in the rumen of sheep fed silage and maize grains from an insect-resistant maize line. A 1914-bp DNA fragment containing the entire coding region of the synthetic cryIA(b) gene was still amplifiable from rumen fluid sampled 5 h after feeding maize grains. The same target sequence, however, could not be amplified from rumen fluid sampled from sheep fed silage prepared from the genetically modified maize line.

The fate of antibiotic resistance marker genes in transgenic plant feed material fed to chickens.

We have examined the fate of an antibiotic resistance marker, incorporated into transgenic maize when fed to chicks. Plant-derived markers were found in the crops of five birds fed transgenic maize and in the stomach contents of two birds. The plant-derived marker gene was not found in the intestines.