Bacterial insecticides The Photorhabdus genome yields novel compounds active against pathogen-
bearing insects By Cathy Holding
One means of controlling the spread of human pathogens and parasites that are spread by insect vectors-
for example, malaria-is the use of insecticides. This approach is frequently compromised by the
acquisition of resistance to the chemicals by the target insects, and novel, efficacious compounds
are difficult to identify and expensive to develop. In the October 5 Nature Biotechnology Eric
Duchaud and colleagues at the Institut Pasteur report the whole genome sequence of the bacterium
Photorhabdus luminescens and describe two loci-encoding proteins that are lethal to the mosquitoes
Anopheles gambiae, Culex pipiens, and Aedes aegyptae. Further sequences encoding a number of toxins
and antibiotics were identified that may provide biotechnological leads in other areas (Nature
Biotechnology, DOI:10.1038/nbt886, October 5, 2003).
Read the rest at The Scientist.com biomedcentral.com03Open ↗
Mitochondrial ribosome structure mapped 3D cryoelectronics reveal unexpected functional roles for
mitoribosomal proteins By David Secko
Mammalian ribosomes exist in two forms: cytoplasmic ribosomes and mitochondrial ribosomes (mitoribosomes)-
which produce proteins critical for mitochondrial function. Since mitochondria are believed to have
arisen from endosymbiosis of a eubacterium, it had been assumed that the mitoribosome would be
structurally more closely related to bacterial ribosomes, but they were observed to have a protein-to-
RNA ratio of 69% protein:31% RNA, almost a complete reversal of the 33% protein:67% RNA in bacterial
ribosomes. This increase in protein content and/or size is thought to be compensation for truncated
rRNA segments found in mitoribosomes, but the evidence for this assumption has been elusive. In the
October 3 Cell, Manjuli R. Sharma and colleagues at the New York State Department of Health report a
cryoelectron microscopic (cryo-EM) map of a mitoribosome that suggests that instead of compensating,
many of the proteins occupy novel positions in the mitoribosome (Cell, 115:97-108, October 3, 2003).
Bacterial protein secretion updated A novel vesicle-mediated pathogenic protein secretion pathway in
gram-negative bacteria By Andrea Rinaldi
Bacterial interaction with plants and animals, symbiotic or pathogenic, involves the transfer to
host cells and tissues of a range of bacterial proteins whose biochemical activities are key to
establishing both commensalism and infection. Export of protein molecules across the bacterial
membranes takes place via a variety of mechanisms, from simple one-component systems to complex
multicomponent pathways, with five types of nonhomologous protein secretion system characterized in
pathogenic bacteria so far. In the October 3 Cell, Sun Nyunt Wai and colleagues at Umeå University
describe an additional protein transfer strategy in gram-negative bacteria that furthers our
understanding of host-bacteria interactions (Cell, 115:25-35, October 3,
2003).
Kind Regards, Robert Karl Stonjek.