Physiological role of tryptophanase in control of tryptophan biosynthesis in Bacillus alvei

Hoch, J. A. (University of Illinois, Urbana), and R. D. DeMoss. Physiological role of tryptophanase in control of tryptophan biosynthesis in Bacillus alvei. J. Bacteriol. 91:667-672. 1966.-Indole excretion occurred early in the exponential growth phase, and derived mainly from biosynthetic intermediates of tryptophan. Tryptophan cleavage by tryptophanase contributed about 1.5% of the indole excreted. In the presence of exogenous tryptophan (5 to 10 mug/ml), excretion of early indole was not observed. Experiments with isotopically labeled indole and tryptophan showed that a low rate of endogenous tryptophan biosynthesis occurred constantly during growth. Both exogenously and endogenously supplied tryptophan were degraded by tryptophanase. As a consequence, the intracellular tryptophan concentration appeared to be maintained at a constant low level. It was suggested that the action of tryptophanase is an example of an enzymatic mechanism which controls the level of a specific metabolite pool.     

Twitching motility and biofilm formation are associated with tonB1 in Xylella fastidiosa

A mutation in the Xylella fastidiosa tonB1 gene resulted in loss of twitching motility and in significantly less biofilm formation as compared with a wild type. The altered motility and biofilm phenotypes were restored by complementation with a functional copy of the gene. The mutation affected virulence as measured by Pierce's disease symptoms on grapevines. The role of TonB1 in twitching and biofilm formation appears to be independent of the characteristic iron-uptake function of this protein. This is the first report demonstrating a functional role for a tonB homolog in X. fastidiosa .     

Surface motility and associated surfactant production in Agrobacterium vitis

Aims:  Agrobacterium vitis is the causal agent of crown gall of grapevine. Surface motility (swarming), an important mechanism for bacterial colonization of new environments and a previously unknown behaviour of Ag. vitis , was demonstrated.
Methods:  Surface motility assays were performed on half-strength potato dextrose agar (Difco) containing 0·75% agar. To test for surfactant production, a drop-collapse test was used. Quorum-sensing (QS) negative and complemented mutants were tested for swarming activity.
Results:  Ninety-one Agrobacterium strains representing – Agrobacterium tumefaciens (17 strains), Agrobacterium rhizogenes (14 strains) and Ag. vitis (60 strains) were tested for swarming and production of surfactant. All Ag. vitis strains expressed a surface-related motility. In contrast, none of 17 strains of Ag. tumefaciens or 14 strains of Ag. rhizogenes exhibited this behaviour. Surface motility in Ag. vitis was associated with surfactant secretion; both of which are regulated by a QS system previously associated with induction of a hypersensitive response on tobacco and necrosis on grape. An aviR (belongs to luxR family) mutant was surface motility negative and did not produce surfactant. An avsI mutant (autoinducer synthase) was also surface motility negative and was complemented with an Ag. tumefaciens clone expressing avsI .
Conclusions:  Agrobacterium vitis is able to produce a characteristic swarming phenotype that is regulated by a complex QS system.
Significance and Impact of the Study:  Swarming activity is unique to Ag. vitis among Agrobacterium sp. and may be associated with the ability of the pathogen to colonize grapevines.     

Phylogeny of a new supertribe Cephenniitae with generic review of Eutheiini and description of a new tribe Marcepaniini (Coleoptera: Staphylinidae: Scydmaeninae)

Genera of Eutheiini are reviewed and Eutheimorphus is removed from this tribe of ant‐like stone beetles (Scydmaeninae) and transferred to Cephenniini. A monogeneric Marcepaniini trib.n. is described to accommodate Marcepania gen.n. from Malaysia, with five species: M. semengohensis sp.n. (the type species of Marcepania), M. tuberculata sp.n. , M. seramaensis sp.n. , M. minutissima sp.n. and M. elongata sp.n. A phylogenetic analysis of all genera of Cephenniini, Eutheiini and Marcepaniini based on adult morphological characters resulted in recovering a well‐supported monophyletic clade Eutheiini + (Marcepaniini + Cephenniini) and these tribes are included in Cephenniitae stat.n. (Eutheiini and Cephenniini are therefore removed from Scydmaenitae). Only a weak support for monophyly of Eutheiini was found, but morphological characters allow for maintaining this presumably relic group as a separate tribe. Previously proposed monophyletic groups within Cephenniini were recovered as such, but after inclusion of Eutheimorphus, a sister taxon to the ‘Cephennomicrus group’, the latter lineage gained weak statistical support. The evolutionary history of Cephenniitae is discussed, with focus on known northern hemisphere fossils classified in Scydmaenitae and Hapsomelitae, but possibly closely allied to Cephenniitae. Establishing the supertribe Cephenniitae is the first step toward a profound reclassification of Scydmaeninae on a robust phylogenetic basis. This published work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub:B0E1B12D-9587-4C4F-A908-A12A0C424A8C .