Aquatic Science

South Florida (USA) has a subtropical to tropical climate with an extensive and diverse coastline that supports the growth of benthic cyanobacterial mats (BCMs). These BCMs are widespread and potentially house numerous bioactive compounds; however, the extent of the cyanobacterial diversity within these mats remains largely unknown. To elucidate this diversity, BCMs from select locations in South Florida were sampled and isolated into unicyanobacterial cultures for morphological and molecular studies. Phylogenetic relationships of isolated taxa were assessed using the markers 16S rRNA and 16S‐23S rRNA ITS by both maximum likelihood and Bayesian inference. We propose Affixifilum gen. nov. based on morphological characteristics and the 16S rRNA phylogeny. Two species are included: Affixifilum granulosum comb nov. (=Neolyngbya granulosa) found in Brazil and Florida (USA) and A. floridanum sp. nov. Several other features, including pair‐wise distance of 16S rRNA and 16S‐23S rRNA ITS, 16S‐23S rRNA ITS secondary structure, morphology, and ecology, provide support for Affixifilum. We also propose the transfer of Lyngbya regalis to Neolyngbya as N. regalis comb. nov. and include the description of one novel species, N. biscaynensis sp. nov.

La presencia de sistemas flagelares es común en muchas bacterias de vida libre, sin embargo, estos han sido considerados ausentes en bacterias del orden Rickettsiales. Candidatus Hepatobacter penaei es una bacteria Rickettsial de origen marino descrita como un microorganismo con motilidad, propulsada por un sistema flagelar, el cual también facilita la infección. Siendo esta bacteria uno de los principales riesgos de infección en granjas camaronícolas. El objetivo de este trabajo fue determinar la presencia de genes que codifiquen proteínas del sistema flagelar de la bacteria Candidatus Hepatobacter penaei. Para el análisis se utilizó la secuencia genómica la base de datos del GenBank con número de acceso NZ_JQAJ00000000.1, una vez detectados los genes, se dedujeron las secuencias de aminoácidos. Las secuencias de aminoácidos del sistema flagelar se identificaron mediante BlastP, por medio de un alineamiento múltiple de dominios conservados. Posteriormente, se realizó un modelado de la proteína FlhA y se comparó con la proteína reportada para Oceanibaculum indicum para la conformación hojas  y  hélices. Los resultados mostraron la presencia de algunas secuencias de aminoácidos relacionadas con los genes del sistema flagelar de la bacteria como MotA, FliG, FliN, FliL FlhA, FlhB, FliQ, FliR y FliF. Finalmente, estos resultados sugieren que Candidatus Hepatobacter penaei es una bacteria tipo Rickettsia que posee un sistema flagelar, el cual posiblemente le confiere motilidad y forma parte del proceso de infección en hospederos como crustáceos marinos.

The systematics of single‐celled cyanobacteria represents a major challenge due to morphological convergence and application of various taxonomic concepts. The genus Cyanothece is one of the most problematic cases, as the name has been applied to oval‐shaped coccoid cyanobacteria lacking sheaths with little regard to their phylogenetic position and details of morphology and ultrastructure. Hereby we analyze an extensive set of complementary genetic and phenotypic evidence to disentangle the relationships among these cyanobacteria. We provide diagnostic characters to separate the known genera Cyanothece, Gloeothece, and Aphanothece, and provide a valid description for Crocosphaera gen. nov. We describe two new genera, Rippkaea and Zehria, to characterize two distinct phylogenetic lineages outside the previously known genera. We further describe 13 new species in total including Cyanothece svehlovae, Gloeothece aequatorialis, G. aurea, G. bryophila, G. citriformis, G. reniformis, Gloeothece tonkinensis, G. verrucosa, Crocosphaera watsonii, C. subtropica, C. chwakensis, Rippkaea orientalis, and Zehria floridana to recognize the intrageneric diversity as rendered by polyphasic analysis. We discuss the close relationship of free‐living cyanobacteria from the Crocosphaera lineage to nitrogen‐fixing endosymbionts of marine algae. The current study includes several experimental strains (Crocosphaera and “Cyanothece”) important for the study of diazotrophy and the global oceanic nitrogen cycle, and provides evidence suggesting ancestral N2‐fixing capability in the chroococcalean lineage.

AbstractChlamydial infections are recognised as causative agent of epitheliocystis, reported from over 90 fish species. In the present study, the farmed striped catfish Pangasianodon hypophthalmus (14–15 cm, 70–90 g) with a history of cumulative mortality of about 23% during June and July 2015, were brought to the laboratory. The histopathological examination of gills from the affected fish revealed presence of granular basophilic intracellular inclusions, mostly at the base of the interlamellar region and in gill filaments. A concurrent infection with Trichodina spp., Ichthyobodo spp. and Dactylogyrus spp. was observed in the gills. The presence of chlamydial DNA in the gills of affected fish was confirmed by amplification and sequencing of 16S rRNA gene. BLAST‐n analysis of these amplicons revealed maximum similarity (96%) with Candidatus Actinochlamydia clariae. On the basis of phylogenetic analysis, it was inferred that the epitheliocystis agents from striped catfish were novel and belonged to the taxon Ca. Actinochlamydia. It is proposed that epitheliocystis agents from striped catfish will be named as Ca. Actinochlamydia pangasiae. The 16S rRNA gene amplicons from novel chlamydiae were labelled and linked to inclusions by in situ hybridisation. This is the first report of epitheliocystis from India in a new fish host P. hypophthalmus.

A recently described symbiosis between the metabolically streamlined nitrogen‐fixing cyanobacterium UCYN‐A and a single‐celled eukaryote prymnesiophyte alga is widely distributed throughout tropical and subtropical marine waters, and is thought to contribute significantly to nitrogen fixation in these regions. Several UCYN‐A sublineages have been defined based on UCYN‐A nitrogenase (nifH) sequences. Due to the low abundances of UCYN‐A in the global oceans, currently existing molecular techniques are limited for detecting and quantifying these organisms. A targeted approach is needed to adequately characterize the diversity of this important marine cyanobacterium, and to advance understanding of its ecological importance. We present findings on the distribution of UCYN‐A sublineages based on high throughput sequencing of UCYN‐A nifH PCR amplicons from 78 samples distributed throughout many major oceanic provinces. These UCYN‐A nifH fragments were used to define oligotypes, alternative taxonomic units defined by nucleotide positions with high variability. The data set was dominated by a single oligotype associated with the UCYN‐A1 sublineage, consistent with previous observations of relatively high abundances in tropical and subtropical regions. However, this analysis also revealed for the first time the widespread distribution of the UCYN‐A3 sublineage in oligotrophic waters. Furthermore, distinct assemblages of UCYN‐A oligotypes were found in oligotrophic and coastally influenced waters. This unique data set provides a framework for determining the environmental controls on UCYN‐A distributions and the ecological importance of the different sublineages.