Photorhabdus is a virulent pathogen that kills its insect host by overcoming immune responses. The bacterium also secretes a range of antibiotics to suppress the growth of other invading microorganisms. Here we show that Photorhabdus produces a small-molecule antibiotic (E)-1,3-dihydroxy-2-(isopropyl)-5-(2-phenylethenyl)benzene (ST) that also acts as an inhibitor of phenoloxidase (PO) in the insect host Manduca sexta. The Photorhabdus gene stlA encodes an enzyme that produces cinnamic acid, a key precursor for production of ST, and a mutation in stlA results in loss of ST production and PO inhibitory activity, which are both restored by genetic complementation of the mutant and also by supplying cinnamic acid. ST is produced both in vitro and in vivo in sufficient quantities to account for PO inhibition and is the only detectable solvent-extractable inhibitor. A Photorhabdus stlA ؊ mutant is significantly less virulent, proliferates slower within the host, and provokes the formation of significantly more melanotic nodules than wild-type bacteria. Virulence of the stlA ؊ mutant is also rescued by supplying cinnamic acid. The proximate cause of the virulence effect, however, is the inhibition of PO, because the effect of the stlA ؊ mutation on virulence is abolished in insects in which PO has been knocked down by RNA interference (RNAi). Thus, ST has a dual function both as a PO inhibitor to counter host immune reactions and also as an antibiotic to exclude microbial competitors from the insect cadaver.Photorhabdus luminescens ͉ RNA interference ͉ stilbene ͉ virulence

The tenS gene encoding tenellin synthetase (TENS), a 4239-residue polyketide synthase nonribosomal-peptide synthetase (PKS-NRPS) from Beauveria bassiana, was expressed in Aspergillus oryzae M-2-3. This led to the production of three new compounds, identified as acyl tetramic acids, and numerous minor metabolites. Consideration of the structures of these compounds indicates that the putative C-terminal thiolester reductase (R) domain does not act as a reductase, but appears to act as a Dieckmann cyclase (DKC). Expression of tenS in the absence of a trans-acting ER component encoded by orf3 led to errors in assembly of the polyketide component, giving clues to the mode of programming of highly reducing fungal PKS. Coexpression of tenS with orf3 from the linked gene cluster led to the production of a correctly elaborated polyketide. The NRPS adenylation domain possibly shows the first identified fungal signature sequences for tyrosine selectivity.

In this study, we monitored the thermal formation of early ribose-glycine Maillard reaction products over time by ion cyclotron resonance mass spectrometry. Here, we considered sugar decomposition (caramelization) apart from compounds that could only be produced in the presence of the amino acid. More than 300 intermediates as a result of the two initial reactants were found after ten hours (100 °C) to participate in the interplay of the Maillard reaction cascade. Despite the large numerical variety the majority of intermediates follow simple and repetitive reaction patterns. Dehydration, carbonyl cleavage, and redox reactions turned out to have a large impact on the diversity the Maillard reaction causes. Although the Amadori breakdown is considered as the main Maillard reaction pathway, other reactive intermediates, often of higher molecular weight than the Amadori rearrangement product, contribute to a large extent to the multitude of intermediates we observed.

Heterologous expression of key components of the Magnaporthe grisea ACE1 gene cluster produces a potential precursor of cryptic avirulence signalling compounds that induce resistance to M. grisea in rice.

A retrospective medical record review was conducted to identify factors from veterinary clinic medical records that may have contributed to suspected ineffectiveness of a heartworm preventive product. Patient records of 271 dogs, comprising 301 instances of positive heartworm antigen test results while the dogs were receiving heartworm preventive were evaluated. Nineteen veterinary practices in 17 counties and parishes in Arkansas, Louisiana, Mississippi, and Tennessee participated in the study. Records were selected by the veterinary clinics as representative of cases of suspected lack of effectiveness for a heartworm preventive, and for which an owner satisfaction claim had been filed with the manufacturer. Medical record data were entered into a software program, and a graphic representation was created to facilitate analysis of whether pet owners had purchased sufficient heartworm preventive for the dog to be compliant during the period when infection with Dirofilaria immitis could have led to the positive heartworm antigen test result for that patient ("window of infection"). In 243 (80.7%) cases, there was insufficient heartworm preventive purchased, leading to a gap in protection during the "window of infection". In only five cases (1.7%) there were no purchase lapses or extenuating circumstances (underdosing of medication, multiple purchase gaps outside the established window of infection, or dogs have been diagnosed with heartworm infection more than once during the period studied). Half the cases were from multiple-dog households, and in many of these households, sharing of product between pets was acknowledged. In another 28% of the cases from multiple-dog households, more product was purchased than was needed for one dog, suggesting that the product was being shared between more than one pet. In most cases, there was at least one reason that a dog did not receive sufficient heartworm preventive product, placing the dog at risk of developing an infection with mature heartworms. Several actions were identified that veterinary clinics can take to improve heartworm disease prevention in their patients.

Reactions between sugars and amino acids in the Maillard reaction produce a multitude of compounds through interconnected chemical pathways. The course of the pathways changes depending on the nature of the amino acids and sugars as well as the processing conditions (e.g. temperature, water activity). Some partial pathways have been elucidated using labelled precursors but the process is very time intensive. Here, we use rapid, non-targeted analysis with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) to deliver the molecular formulae and ion intensities of the compounds generated from reaction of four amino acids with ribose (10 h at 100 °C) to study the effect of amino acid side chains on the reaction pathways. Using van Krevelen diagrams, known chemical changes during the reaction (e.g. dehydration or decarboxylation) can be studied. Comparison of the data from the four amino acids studied, showed a common pathway, which involved 73 Maillard reaction products (MRPs) where the differences were due only to the nature of the amino acid side chain. From the more than 1400 different molecular formulae found, pathways unique to the amino acids were also identified and the order of reactivity was lysine >cysteine >isoleucine ≈ glycine. While unequivocal identification of the compounds cannot be achieved with FT-ICR-MS, applying known chemical transformations found in the Maillard reaction, not only identifies new and known pathways, but also integrates the MRPs into a general Maillard reaction scheme that better represents the totality of the Maillard reaction.

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