Oxidation of long-chain alkanes by Acetobacter rancens

Summary The degradation of hexadecane and tetradecane by Acetobacter rancens CCM 1774 was investigated. It was found that this strain is able to grow to a limited extent on hexadecane as a carbon source. The occurrence of n-alkanoic acids and alcohols among the reaction products of growing as well as resting cells indicates a monoterminal degradation of long-chain alkanes. Both alkane-grown and glucose-grown resting cells exhibited alkane oxidizing activities which were not influenced by chloramphenicol. This suggested a constitutive nature of the appropriate enzymes.     

Purification and properties of carnitine dehydratase from Escherichia coli--a new enzyme of carnitine metabolization

Carnitine dehydratase from Escherichia coli 044 K74 is an inducible enzyme detectable in cells grown anaerobically in the presence of L(-)-carnitine or crotonobetaine. It has been purified 500-fold to electrophoretic homogeneity by chromatography on phenyl-Sepharose, hydroxyapatite, DEAE-Sepharose, second phenyl-Sepharose and finally gel filtration on a Sephadex G-100 column. During the purification procedure a low-molecular-weight effector essential for enzyme activity was separated from the enzyme. The addition of this still unknown effector caused reactivation of the apoenzyme. The relative molecular mass of the apoenzyme has been estimated to be 85,000. It seems to be composed of two identical subunits with a relative molecular mass of 45,000. The purified and reactivated enzyme has been further characterized with respect to pH and temperature optimum (7.8 and 37-42 degrees C), equilibrium constant (Keq = 1.5 +/- 0.2) and substrate specifity. The enzyme is inhibited by thiol reagents. The Km value for crotonobetaine is 1.2.10(-2) M. gamma-Butyrobetaine, D(+)-carnitine and choline are competitive inhibitors of crotonobetaine hydration.     

Natural history and foraging behavior of the carpenter ant Camponotus sericeiventris Guérin, 1838 (Formicinae, Campotonini) in the Brazilian tropical savanna

Camponotus sericeiventris is a polymorphic ant living in populous colonies at tropical forests and cerrado formation. This study provides a detailed account of the natural history and foraging biology of C. sericeiventris in cerrado at Ecological Station of Panga, Southeast of Brazil. The nest distribution according to vegetation physiognomies, activity rhythm, diet, and foraging patterns were described. Results showed that nests occur inside dead or live trunks, and also in branches of soft wood at cerradão and gallery forest physiognomies (approximately 1 nest/100m²), but not in the mesophytic forest. Ant activity is correlated with temperature and humidity. There is overlap in the foraging area among neighbor colonies (as far as 28 m) without evidence of agonistic interactions. Foragers leave the nest independently or in groups and frequently searched for food individually. Workers are generalistic feeders visiting flowers and extrafloral nectaries, attending Hemiptera (aphids and membracids) and Lepidoptera (Lycaenidae larvae), collecting seeds and fruits, and hunting for live preys as well as scavenging for dead animals. The great number of interactions with different plant and animals suggests that this species has an important participation in the interaction web in this environment.     

Microlicia crassa and M. maculata spp. nov. (Melastomataceae) from Minas Gerais,Brazil: morphology and leaf anatomy

Two new species of Microlicia from campos rupestres of Minas Gerais are described, illustrated and compared with their relatives. Microlicia crassa sp. nov. is similar to M. formosa, and M. maculata sp. nov. is similar to M. isophylla and M. tetrasticha. The trichomes covering both surfaces of the leaves of the two new species and their relative, M. isophylla may be characterized as sessile glands under a stereomicroscope, but anatomical studies revealed the presence of a short stalk. Microlicia crassa and M. maculata are assessed as “Endangered”, according to the IUCN categories and criteria.