Publications

4359

Summary A novel moderately thermophilic, facultatively anaerobic chemoorganotrophic bacterium strain P3M ‐2 T was isolated from a microbial mat developing on the wooden surface of a chute under the flow of hot water (46° C ) coming out of a 2775‐m‐deep oil exploration well ( T omsk region, R ussia). Strain P3M ‐2 T is a moderate thermophile and facultative anaerobe growing on mono‐, di‐ or polysaccharides by aerobic respiration, fermentation or by reducing diverse electron acceptors [nitrite, F e( III ), As ( V )]. Its closest cultivated relative (90.8% rRNA gene sequence identity) is I gnavibacterium album , the only chemoorganotrophic member of the phylum C hlorobi . New genus and species M elioribacter roseus are proposed for isolate P3M ‐2 T . Together with I . album , the new organism represents the class I gnavibacteria assigned to the phylum Chlorobi . The revealed group includes a variety of uncultured environmental clones, the 16S rRNA gene sequences of some of which have been previously attributed to the candidate division ZB1 . Phylogenetic analysis of M . roseus and I . album based on their 23S rRNA and RecA sequences confirmed that these two organisms could represent an even deeper, phylum‐level lineage. Hence, we propose a new phylum Ignavibacteriae within the Bacteroidetes – C hlorobi group with a sole class I gnavibacteria , two families I gnavibacteriaceae and M elioribacteraceae and two species I . album and M . roseus . This proposal correlates with chemotaxonomic data and phenotypic differences of both organisms from other cultured representatives of C hlorobi . The most essential differences, supported by the analyses of complete genomes of both organisms, are motility, facultatively anaerobic and obligately organotrophic mode of life, the absence of chlorosomes and the apparent inability to grow phototrophically.

This article describes the first detection of Cytauxzoon felis, using molecular techniques, in a naturally infected domestic cat from Brazil, South America. Coinfection with 'CandidatusMycoplasma haemominutum' was also found. The molecular identification of the piroplasmid species was performed by Polymerase Chain Reaction (PCR) and sequencing analysis. A 284 pb fragment of the gene encoding the 18S ribosomal RNA region was amplified and showed 99% identity with other C. felis strains from North America. In addition, PCR-RFLP (restriction fragment length polymorphism) analysis, which amplifies a 595 bp fragment of the gene encoding 16S ribosomal RNA of some bacterial species, identified the co-infecting species as 'Candidatus M. haemominutum'.

This work characterizes a unicellular cyanobacterium with nearly spherical cells and thin-outlined sheaths that divide irregularly, forming small packets immersed in a diffluent mucilaginous layer. It was isolated growing on calcite speleothems and walls in a show cave in Collbató (Barcelona, Spain). Spectral confocal laser and transmission electron microscopy were used to describe the morphology, fine structure and thylakoid arrangement. The pigments identified were phycoerythrin, phycocyanin, allophycocyanin and chlorophyll a. Three-dimensional reconstructions, generated from natural fluorescence z-stacks, revealed a large surface area of nearly flat, arm-like thylakoidal membranes connected to each other and forming a unified structure in a way that, to our knowledge, has never been described before. Phylogenetic analyses using the 16S rRNA gene sequence showed 95 % similarity to strain Chroococcus sp. JJCM (GenBank accession no. AM710384). The diacritical phenotypic features do not correspond to any species currently described, and the genetic traits support the strain being classified as the first member of an independent genus in the order Chroococcales and the family Chroococcaceae. Hence, we propose the name Chalicogloea cavernicola gen. nov., sp. nov. under the provisions of the International Code of Nomenclature for Algae, Fungi and Plants. The type strain of Chalicogloea cavernicola is COLL 3T ( = CCALA 975T  = CCAP 1424/1T).

‘Candidatus Liberibacter asiaticus’ is the bacterium implicated as a causal agent of the economically damaging disease of citrus called huanglongbing (HLB). Vertical transmission of the organism through seed to the seedling has not been demonstrated. Previous studies using real-time polymerase chain reaction assays indicated abundant bacterial 16S rRNA sequences in seed coats of citrus seed but the presence of intact bacterial cells was not demonstrated. We used microscopy to verify that intact bacterial cells were present in citrus seed coats. Bacterial cells with the morphology and physical dimensions appropriate for ‘Ca. L. asiaticus’ were seen in phloem sieve elements in the vascular bundle of grapefruit seed coats using transmission electron microscopy (TEM). Fluorescence in situ hybridization (FISH) analyses utilizing probes complementary to the ‘Ca. L. asiaticus’ 16S rRNA gene revealed bacterial cells in the vascular tissue of intact seed coats of grapefruit and pummelo and in fragmented vascular bundles excised from grapefruit seed coats. The physical measurements and the morphology of individual bacterial cells were consistent with those ascribed in the literature to ‘Ca. L. asiaticus’. No bacterial cells were observed in preparations of seed from fruit from noninfected trees. A small library of clones amplified from seed coats from a noninfected tree using degenerate primers targeting prokaryote 16S rRNA gene sequences contained no ‘Ca. L. asiaticus’ sequences, whereas 95% of the sequences in a similar library from DNA from seed coats from an infected tree were identified as ‘Ca. L. asiaticus’, providing molecular genetic corroboration that the bacterial cells observed by TEM and FISH in seed coats from infected trees were ‘Ca. L. asiaticus’.