Motile chemosensory behaviour of phagotrophic protists: mechanisms for and efficiency in congregating at food patches

Phagotrophic protists are capable of congregating at point sources of food within a few minutes, from distances of up to several cm in the case of ciliates, or several mm in the case of microflagellates. This is exemplified by four ciliate species and a heterotrophic flagellate. Congregation is accomplished by the combined effect of more than one type of chemosensory motile behaviour including "kinetic responses", "temporal-gradient sensing", and "helical klinotaxis". The results are discussed in terms of microscale patchiness in nature.     

Neptuniibacter pectenicola sp. nov. and Neptuniibacter marinus sp. nov., two novel species isolated from a Great scallop (Pecten maximus) hatchery in Norway and emended description of the genus Neptuniibacter.

Nine isolates obtained from a great scallop hatchery in Norway were characterized using a polyphasic approach. Strains were Gram-negative, aerobic and motile rods with oxidative metabolism. Phylogenetic analysis based on the sequences of 16S rRNA and rpoB genes showed that these strains formed two different groups associated with members of the genus Neptuniibacter. DNA–DNA hybridization (DDH) and Average Nucleotide Identity (ANI) demonstrated that the isolates constituted two novel species of this genus, which can be phenotypically differentiated from their closest relatives. The names Neptuniibacter marinus sp. nov. and Neptuniibacter pectenicola sp. nov are proposed, with ATR 1.1^T (=CECT 8938^T = DSM 100783^T) and LFT 1.8^T (=CECT 8936^T = DSM 100781^T) as respective type strains.     

Cuticle-catalyzed coupling between polyamino acids and N-acetyldopamine

N-[2-¹⁴C]Acetyldopamine (NADA) was incubated in vitro with a series of homopolyamino acids or proteins in the presence of cell-free cuticle from locusts. The oxidized NADA was bound to the materials in varying degrees. The results indicate that lysine and histidine sidechains in the cuticular proteins might be the most likely candidates as participants in the crosslinking process in agreement with the results obtained by NMR.     

V-ATPase is a major component of the Golgi complex in the scaly green flagellate Scherffelia dubia

Highly purified membranes isolated from the Golgi complex of the scaly green flagellate Scherffelia dubia (Chlorophyta) were subjected to Triton X-114 two-phase partitioning. Proteins in the detergent phase were analyzed by 2D gel electrophoresis and a major protein of 66 kD (p66) was N-terminally sequenced. The complete cDNA sequence of p66 was obtained by 3' RACE-PCR and screening of a cDNA library of S. dubia with a PCR probe derived from the 3' RACE. Sequence analysis of the cDNA clone identified p66 as subunit A of V-ATPase. Other major proteins in the isolated Golgi complex were immunoreactive to heterologous antibodies raised against subunit B or the holoenzyme of V-ATPase. A polyclonal (anti-p66) antibody raised against a recombinant, bacterially expressed p66 fusion protein recognized p66 in the isolated Golgi complex in western blots and localized the antigen by immunogold electron microscopy mostly to the scale reticulum but also to the Golgi stack within the Golgi complex. Concanamycin A-sensitive (but bafilomycin A1-insensitive) ATPase activity was present in the isolated Golgi complex, and monensin at 0.5-1 microM reversibly inhibited flagellar regeneration and resulted in swelling of Golgi cisternae. It is concluded that a functional V-ATPase is a major protein of the Golgi complex in S. dubia and is presumably associated with sorting processes at the endocytotic/exocytotic boundary of the Golgi complex.     

Protozoal sequences may reveal additional isoforms of the 14-3-3 protein family

The phylogenetic position of eleven 14-3-3 proteins from five protozoal species was tested relative to other eukaryotic 14-3-3 versions representing many of the previously described isoforms. The protozoal proteins, four from Entodinium caudatum, three from Entameoba histolytica and four from apicomplexan parasites formed clusters closer to the plant and animal epsilon isoforms than to the animal beta, gamma/eta, sigma/theta, and zeta isoforms. This extends the preliminary findings of Wang and Shakes (1996) but data from a wider range of genera are still required to strengthen our hypothesis that the protozoan isoforms may constitute novel isoforms of the 14-3-3 family.