Photobacterium damselae subsp. piscicida: an integrated view of a bacterial fish pathogen

Pasteurellosis, or pseudotuberculosis, is a bacterial septicaemia caused by the halophilic bacterium Photobacterium damselae subsp. piscicida (formerly Pasteurella piscicida). Although this disease was first described in wild populations of white perch and striped bass, currently the natural hosts of the pathogen are a wide variety of marine fish. The disease has great economic impact bothin Japan, where it affects mainly yellowtail cultures, and in the Mediterranean area, due to the losses it causes in seabream and seabass farms. This microorganism serves as a perfect model to study a bacterial fish pathogen, either at an applied level, to resolve or to mitigate the high economic losses of fish farmers, or at a basic level, for a better understanding of P. damselae subsp. piscicida biology. This article discusses the methods employed in our laboratory to study the causative agent of pasteurellosis. It reviews important aspects, from the diverse procedures for the detection and isolation of the pathogen to the latest molecular studies that have allowed its correct taxonomic allocation. Characterization of some virulence mechanisms and the available methods to prevent the disease are also presented

Editorial: Microbial Taxonomy, Phylogeny and Biodiversity

The great diversity of microbial life is the remaining majorreservoir of unknown biologicaldiversity on Earth. To understand this vast, but largely unperceived diversity with its untappedgenetic, enzymatic and industrial potential, microbial systematics is undergoing a revolutionarychange in its approach to describe novel taxa based on genomic/envirogenomic information(Rosselló-Móra and Whitman, 2019)S

From the Gene Sequence to the Phylogeography through the Population Structure: The Cases of Yersinia ruckeri and Vibrio tapetis

Multilocus sequence analysis (MLSA) and multilocus sequence typing (MLST) are nowadays considered as gold standards in the study of microbial systematic, being both techniques based on the interpretation of the sequences of several housekeeping genes. In this context, the sequences can be analyzed from different points of view. On the one hand, the phylogeny of the bacterial species can be estimated using the MLSA approach and on the other hand, the structure of the population can be inferred by means of MLST. Moreover, most species display some degree of population structure that can be interpreted in geographic and chronological contexts, that is, phylogeographic studies. In this review, the phylogeny and population structure of two important fish and shellfish pathogens, Yersinia ruckeri and Vibrio tapetis, exhibiting very different evolutive patterns will be analyzed. In both cases, the species form robust and monophyletic groups from a phylogenetic point of view. Regarding to the population structure, very different results were found. While Y. ruckeri follows an epidemic model of clonal expansion with well‐adapted clones that explode to be widely distributed, V. tapetis appears to have a mixed structure in where the paradox of clonality and high level of variability coexist. Furthermore, phylogeographical studies provided the evolutionary and geographical context for the species, allowing the determination of historical and spatial influences on the diversification of both species

Inhibitory activity of Phaeobacter strains against aquaculture pathogenic bacteria

A total of 523 bacterial strains were isolated during a 4-year period from mollusc hatcheries (flat oyster and clams) in Galicia (NW Spain). All of the strains were tested for their antibacterial activity against three larval pathogens (Vibrio anguillarum USC-72, V. neptunius PP-145.98, and Vibrio sp. PP-203). Of the isolates, 52 inhibited at least one of the target strains, and 11 inhibited all of them. The main source of active strains was oyster larvae, followed by water, tank surfaces, spat, and broodstock. Four similar strains, belonging to the genus Phaeobacter, showed the strongest activity. Strain PP-154, selected as representative of this group, displayed a wide spectrum of inhibitory activity against aquaculture pathogens, especially against members of the genus Vibrio, which is responsible for the most larval deaths. The inhibitory ability of such strain on solid medium was confirmed in seawater experiments, and the optimal conditions for antibacterial activity were established. These strains are promising probiotics for aquaculture facilities. Their potential benefit is based on the capacity to control the proliferation of a variety of aquaculture bacterial pathogens in mollusc larval cultures. [Int Microbiol 2009; 12(2):107-114

Bacillota y otros exabruptos

A comienzos de año hubo bastante revuelo mediático en torno a la validación de algunos nombres de filo (Oren y Garrity, 2021) conforme a un cambio reciente (Oren et al., 2021a) en el código de nomenclatura procariota. No faltaron ni siquiera algunos memes como los que reproducimos aquí. En una disciplina como la nomenclatura biológica esto es algo tan infrecuente que conviene aprovecharlo para hacer pedagogía, explicando todos los hechos clave y todos los actores. También desmentir errores: las redes sociales aportan mucha rapidez, pero también menos rigor que otras formas de comunicación

Solar water disinfection (SODIS): Impact on hepatitis A virus and on a human Norovirus surrogate under natural solar conditions

This study evaluates the effectiveness of solar water disinfection (SODIS) in the reduction and inactivation of hepatitis A virus (HAV) and of the human Norovirus surrogate, murine Norovirus (MNV-1), under natural solar conditions. Experiments were performed in 330 ml polyethylene terephthalate (PET) bottles containing HAV or MNV-1 contaminated waters (103 PFU/ml) that were exposed to natural sunlight for 2 to 8 h. Parallel experiments under controlled temperature and/or in darkness conditions were also included. Samples were concentrated by electropositive charged filters and analysed by RT-real time PCR (RT-qPCR) and infectivity assays. Temperature reached in bottles throughout the exposure period ranged from 22 to 40ºC. After 8 h of solar exposure (cumulative UV dose of ~828 kJ/m2 and UV irradiance of ~20 kJ/l), the results showed significant (P < 0.05) reductions from 4.0 (±0.56) ×104 to 3.15 (±0.69) × 103 RNA copies/100 ml (92.1%, 1.1 log) for HAV and from 5.91 (±0.59) × 104 to 9.24 (±3.91) × 103 RNA copies/100 ml (84.4%, 0.81 log) for MNV-1. SODIS conditions induced a loss of infectivity between 33.4% and 83.4% after 4 to 8 h in HAV trials, and between 33.4% and 66.7% after 6 h to 8 h in MNV-1 trials. The results obtained indicated a greater importance of sunlight radiation over the temperature as the main factor for viral reduction. [Int Microbiol 2015; 18(1):41-49]Keywords: Solar water disinfection (SODIS) · water disinfection · hepatitis A virus (HAV) · murine Norovirus (MNV-1

Characterization of the microbiota associated to Pecten maximus gonads using 454-pyrosequencing

A next-generation sequencing (NGS) approach was used to study the microbiota associated to Pecten maximus broodstock, applying pyrosequencing of PCR-amplified V1-V4 16S rRNA gene regions. We analysed the resident bacterial communities in female and male scallop gonads before and after spawning. DNA samples were amplified and quality-filtered reads were assigned to family and genus taxonomic levels using the Ribosomal Database Project classifier. A total of 18,520 sequences were detected, belonging to 13 phyla, including Proteobacteria (55%), Bacteroidetes (11,7%), Firmicutes (3%), Actinobacteria (2%) and Spirochaetes (1,2%), and 110 genera. The major fraction of the sequences detected corresponded to Proteobacteria, Beta- and Gammaprotebacteria being the most abundant classes. The microbiota of P. maximus gonad harbour a wide diversity, however differences on male and female samples were observed, where female gonad samples show a larger number of genera and families. The dominant bacterial genera appeared to be Delftia, Acinetobacter, Hydrotalea, Aquabacterium, Bacillus, Sediminibacterium, Sphingomonas, and Pseudomonas that were present among the four analysed samples. This next generation sequencing technique, applied for the first time in P. maximus (great scallop) gonads was useful for the study of the bacterial communities in this mollusc, unravelling the great bacterial diversity in its microbiota. [Int Microbiol 19(2): 93-99(2016)]Keywords: Pecten maximus · gonads microbiota · next-generation sequencing (NGS) · molluscs pathogens · aquacultur

Assessment of human enteric viruses in cultured and wild bivalve molluscs

Standard and real-time reverse transcription-PCR (rRT-PCR) procedures were used to monitor cultured and wild bivalve molluscs from the Ría de Vigo (NW Spain) for the main human enteric RNA viruses, specifically, norovirus (NoV), hepatitis Avirus (HAV), astrovirus (AsV), rotavirus (RT), enterovirus (EV), and Aichi virus (AiV). The results showed the presence of at least one enteric virus in 63.4% of the 41 samples analyzed. NoV GII was the most prevalent virus, detected in 53.7% of the samples, while NoV GI, AsV, EV, and RV were found at lower percentages (7.3, 12.2, 12.2, and 4.9%, respectively). In general, samples obtained in the wild were more frequently contaminated than those from cultured (70.6 vs. 58.3%) molluscs and were more readily contaminated with more than one virus. However, NoV GI was detected in similar amounts in cultured and wild samples (6.4 × 102 to 3.3 × 103 RNA copies per gram of digestive tissue) while the concentrations of NoV GII were higher in cultured (from 5.6 × 101 to 1.5 × 104 RNA copies per gram of digestive tissue) than in wild (from 1.3 × 102 to 3.4 × 104 RNA copies per gram of digestive tissue) samples. [Int Microbiol 2009; 12(3):145-151