Estimating taxonomic and functional structure along a tropical estuary: linking metabolic traits and aspects of ecosystem functioning.

Microbial life forms are among the most ubiquitous on Earth, yet many remain understudied in Caribbean estuaries. We report on the prokaryote community composition of the Urabá Estuary in the Colombian Caribbean using 16S rRNA gene-transcript sequencing. We also assessed potential functional diversity through 38 metabolic traits inferred from 16S rRNA gene data.

Collective behavior and virulence arsenal of the fish pathogen in the biofilm realm.

Piscirickettsiosis is a fish disease caused by the Gram-negative bacterium This disease has a high socio-economic impact on the Chilean salmonid aquaculture industry. The bacterium has a cryptic character in the environment and their main reservoirs are yet unknown. Bacterial biofilms represent a ubiquitous mechanism of cell persistence in diverse natural environments and a risk factor for the pathogenesis of several infectious diseases, but their microbiological significance for waterborne veterinary diseases, including piscirickettsiosis, have seldom been evaluated.

Development of a Multiplex PCR Assay for Genotyping the Fish Pathogen Through Comparative Genomics.

is a bacterial pathogen that severely impact the aquaculture in several countries as Canada, Scotland, Ireland, Norway, and Chile. It provokes Piscirickettsiosis outbreaks in the marine phase of salmonid farming, resulting in economic losses. The monophyletic genogroup LF-89 and a divergent genogroup EM-90 are responsible for the most severe Piscirickettsiosis outbreaks in Chile.

Assessing the impacts of skin mucus from Salmo salar and Oncorhynchus mykiss on the growth and in vitro infectivity of the fish pathogen Piscirickettsia salmonis.

Piscirickettsiosis is a fish disease caused by the facultative intracellular bacterium, Piscirickettsia salmonis. Even though entry routes of P. salmonis in fish are not fully clear yet, the skin seems to be the main portal in some salmonid species.

Improved understanding of biofilm development by Piscirickettsia salmonis reveals potential risks for the persistence and dissemination of piscirickettsiosis.

Piscirickettsia salmonis is the causative agent of piscirickettsiosis, a disease with high socio-economic impacts for Chilean salmonid aquaculture. The identification of major environmental reservoirs for P. salmonis has long been ignored.

Nitrospina bacteria in a rocky intertidal habitat (Quintay Bay, central Chile).

Nitrospina bacteria are among the most important nitrite oxidizers in coastal and open-ocean environments, but the relevance of the genus contrasts with the scarceness of information on their ecophysiology and habitat range. Thus far, Nitrospina bacteria have been the only nitrite oxidizers detected at high abundance in Chilean coastal waters. These levels are often higher than at other latitudes.

Stress Tolerance-Related Genetic Traits of Fish Pathogen in a Mature Biofilm.

is the causative agent of bacterial cold-water disease and rainbow trout fry syndrome, and hence this bacterium is placed among the most important salmonid pathogens in the freshwater aquaculture industry. Since bacteria in biofilms differ substantially from free-living counterparts, this study sought to find the main differences in gene expression between sessile and planktonic states of LM-02-Fp and NCMB1947, with focus on stress-related changes in gene expression occurring during biofilm formation. To this end, biofilm and planktonic samples were analyzed by RNA sequencing to detect differentially expressed candidate genes (DECGs) between the two growth states, and decreasing the effects of interstrain variation by considering only genes with log-fold changes ≤ -2 and ≥ 2 at adj-values ≤ 0.

Different Phenotypes of Mature Biofilm in Share a Potential for Virulence That Differs from Planktonic State.

is the etiological agent of bacterial coldwater disease and the rainbow trout fry syndrome in salmonid aquaculture worldwide. However, there have been few studies into the capacity of to form biofilms and how these cellular accretions differ from planktonic cells or how they affect potential virulence. We evaluated the biofilm formation by three Chilean isolates of (LM-02-Fp, LM-06-Fp, and LM-13-Fp) and two non-Chilean strains (JIP02/86 and NCMB1947), and compared biofilm and planktonic states to obtain insights into expression differences of virulence- and biofilm-related genes (VBRGs).

Variability of nitrifying communities in surface coastal waters of the Eastern South Pacific (∼36° S).

We report the seasonal and single-diurnal variability of potentially active members of the prokaryote community in coastal surface waters off central Chile and the relationship between nitrifiers and solar radiation by combining 16S cDNA-based pyrosequencing, RT-qPCR of specific gene markers for nitrifiers (amoA, for general AOA, AOA-A, AOA-B, Nitrosopumilus maritimus and beta-AOB; and 16S rRNA gene for Nitrospina-like NOB), and solar irradiance measurements. We also evaluated the effects of artificial UVA-PAR and PAR spectra on nitrifiers by RT-qPCR. All nitrifiers (except AOA-B ecotype) were detected via RT-qPCR but AOA was the only group detected by pyrosequencing.

Nitrospina-like bacteria are the main drivers of nitrite oxidation in the seasonal upwelling area of the Eastern South Pacific (Central Chile ∼36°S).

Aerobic nitrite oxidation in marine environments plays a key role in the nitrification process. Marine bacteria involved in this nitrate-producing process have however been seldom studied compared with the ammonia-oxidizing community. Here, we report for the first time the community structure of aerobic nitrite-oxidizing bacteria (NOB) in the seasonal upwelling and oxygen-deficient area off Central Chile.