Characterization and survey in cattle of a rumen Pyrimadobacter sp. which degrades the plant toxin fluoroacetate

ABSTRACT Among the natural halogenic compounds, the plant toxin fluoroacetate (FA) causes livestock fatalities in southern hemisphere countries. Here, we report on the isolation of a rumen bacterium, strain C12–8 that degrades FA under anaerobic conditions. 16S rRNA gene sequence analysis showed this bacterium belonged to the Pyramidobacter genus within the Synergistetes phylum and was 98% similar to Pyramidobacter piscolens W5455 isolated from the human oral cavity. Transmission electron microscopy showed the cell envelope to be unusual, with only one membrane and no obvious external wall. Growth and FA degradation were enhanced by peptide-rich protein hydrolysates but not carbohydrates. End products of metabolism were mainly acetate, propionate/isovalerate and isobutyrate. Strain C12-8 preferentially used peptide-bound amino acids rather than free amino acids. Glycine, serine, threonine, leucine, histidine and isoleucine were utilized as free and peptide-bound amino acids, but there was minimal utilization of alanine, proline, methionine, aspartic acid, lysine and arginine in either form. A survey of several cattle properties in northern Australia showed that strain C12-8 and other FA degrading bacteria affiliated with Cloacibacillus porcorum strain MFA1 were endemic to cattle in the northern beef herd and may help to reduce toxicity.

Pulse optimization for all-optical switching engineered in photonic crystal waveguide with micro-resonator

We have investigated switching properties and especially pulse shape preservation in the process of all-optical switching. To this end, we made two different designs of all-optical switches based on two-dimensional (2D) photonic crystal (PC) waveguides with different dispersive properties and micro-resonators with different quality factors. We realized numerically that all-optical switching without or with marginal temporal pulse distortion can be obtained under precisely chosen conditions on pulse duration and detuning. In particular, the former has to be approximately 2.5 times longer than cavity buildup time and the latter has to be equal to one full width at half maximum of the cavity transmission spectrum.

TWO-PHOTON NONLINEAR SPECTROSCOPY OF PERIODICALLY TRAPPED ULTRACOLD ATOMS IN A CAVITY

We study the transmission spectra of a Bose Einstein condensate (BEC) confined in an optical lattice interacting with two modes of a cavity via nonlinear two-photon transition. In particular, we show that the one-photon and two-photon cavity transmission spectra of a BEC are different. We found that when the BEC is in the Mott state, the usual normal mode splitting present in the one-photon transition is missing in the two-photon interaction. When the BEC is in the superfluid state, the transmission spectrum shows the usual multiple lorentzian structure. However the separation between the lorentzians for the two-photon case is much larger than that for the one-photon case. This study could form the basis for nondestructive high resolution Rydberg spectroscopy of ultracold atoms or two-photon spectroscopy of a gas of ultracold atomic hydrogen.