BackgroundIn the environment as well as in the vertebrate intestine, Listeriae have access to complex carbohydrates like maltodextrins. Bacterial exploitation of such compounds requires specific uptake and utilization systems.Methodology/Principal FindingsWe could show that Listeria monocytogenes and other Listeria species contain genes/gene products with high homology to the maltodextrin ABC transporter and utilization system of B. subtilis. Mutant construction and growth tests revealed that the L. monocytogenes gene cluster was required for the efficient utilization of maltodextrins as well as maltose. The gene for the ATP binding protein of the transporter was located distant from the cluster. Transcription analyses demonstrated that the system was induced by maltose/maltodextrins and repressed by glucose. Its induction was dependent on a LacI type transcriptional regulator. Repression by glucose was independent of the catabolite control protein CcpA, but was relieved in a mutant defective for Hpr kinase/phosphorylase.Conclusions/SignificanceThe data obtained show that in L. monocytogenes the uptake of maltodextrin and, in contrast to B. subtilis, also maltose is exclusively mediated by an ABC transporter. Furthermore, the results suggest that glucose repression of the uptake system possibly is by inducer exclusion, a mechanism not described so far in this organism.

This study reports the occurrence of high diversity of novel frog-biting midges (Diptera: Corethrellidae) from Brunei Darussalam, Borneo. Flies were found feeding on eight species of frogs from five families. Traps using frog calls as lures were used to capture flies in lowland dipterocarp rainforest and peatswamp forest. We identified 11 different fly morphotypes based on gross external morphology and pigmentation. Recognition tests showed that advertisement calls of three frogs, Rana baramica Boettger (brown marsh frog), R. glandulosa Boulenger (rough-sided frog), and Megophrys nasuta Schlegel (Bornean horned toad) were sufficient for fly capture. The degree of host specificity using acoustic lures was weak. However, the proportion of different morphotypes caught at the traps broadcasting R. baramica and R. glandulosa calls differed, suggesting that frogs vary in their attractiveness towards frog-biting midges.