RESUMEN
A novel purple sulfur bacterium, strain AX1YPE(T), was isolated from marine sediments sampled at 47 m depth in Callao Bay, Perú. Strain AX1YPE grew anaerobically, synthesizing bacteriochlorophyll a and carotenoid pigments of the spirilloxanthin series. Cells were Gram-stain-negative rods and actively motile by a polar flagellum. Strain AX1YPE was able to grow photolithoautotrophically with sulfide and thiosulfate as electron donors. This new phototrophic organism utilized ammonium salt, N2, urea and glutamate as nitrogen sources. Strain AX1YPE had a DNA base composition of 63.9 mol% G+C. Analysis of the 16S rRNA gene sequence indicated that strain AX1YPE clusters in a separate branch within the genus Allochromatium of the family Chromatiaceae. Strain AX1YPE showed 16S rRNA gene sequence similarities of 98.2% with Allochromatium vinosum DSM 180(T) and Allochromatium minutissimum DSM 1376(T), 98.1% with Allochromatium phaeobacterium JA144(T), 97.3% with Allochromatium renukae DSM 18713(T) and 96.8% with Allochromatium warmingiiDSM 173(T). DNA-DNA hybridization values to the type strains of its closest relatives, A. vinosum and A. minutissimum, were 59 and 64%, respectively. The predominant fatty acid of strain AX1YPE(T) was C18 : 1ω;7c and it notably possessed C20 : 1 as a minor component. PCR-based molecular typing (Box A1R and randomly amplified polymorphic DNA) produced a unique banding pattern for strain AX1YPE(T) in comparison with the type strains of A. vinosum and A. minutissimum. Based on data from this polyphasic taxonomic study, which also includes average nucleotide identity comparison of five concatenated housekeeping genes, strain AX1YPE(T) is considered to represent a novel species of the genus Allochromatium for which the name Allochromatiumhumboldtianum sp. nov. is proposed. The type strain is AX1YPE(T) ( = DSM 21881(T) = KCTC 15448(T)).
Asunto(s)
Chromatiaceae/clasificación , Sedimentos Geológicos/microbiología , Filogenia , Técnicas de Tipificación Bacteriana , Bacterioclorofila A/metabolismo , Composición de Base , Carotenoides/metabolismo , Chromatiaceae/genética , Chromatiaceae/aislamiento & purificación , ADN Bacteriano/genética , Ácidos Grasos/química , Datos de Secuencia Molecular , Hibridación de Ácido Nucleico , Perú , ARN Ribosómico 16S/genética , Agua de Mar/microbiología , Análisis de Secuencia de ADNRESUMEN
To examine the extent of the microbial food web in suboxic waters of a shallow subtropical coastal lagoon, the density and biomass of bacteria and protozooplankton were quantified under different dissolved oxygen (DO) levels. In addition, bottom waters of a stratified site were compared with bottom waters of a homogeneous site under periods of high and low biological oxygen production/consumption in the lagoon. At the stratified site, microbial biomass decreased with oxygen decline, from oxia to suboxia, with a recovery of the initial total biomass after a 20-day period of persistent suboxia. A peak in density and biomass of purple sulfur bacteria (PSB) (90 µg C L(-1)) occurred in the suboxic waters 20 days prior to the peak in biomass of ciliates >50 µm (Loxophyllum sp. of 150 µm) (160 µg C L(-1)), demonstrating a top down biomass control. Ciliates >50 µm were positively correlated with PSB and bacteriochlorophyll a (photosynthetic pigment of PSB). Total protozoan biomass reached 430 µg C L(-1) in the suboxic waters of the stratified site, with ciliates >50 µm accounting for 90% of the total ciliate biomass and of 55 % of biomass of protozoa. At the homogeneous site, total protozoan biomass was only 66 µg C L(-1), where flagellates and ciliates <25 µm were the dominant microorganisms. Therefore, as light is available for primary producers in the bottom waters of shallow stratified coastal lagoons or estuaries, one can expect that high primary production of PSB may favor a specialized microbial food web composed by larger microorganisms, accessible to zooplankton that tolerate low DO levels.
Asunto(s)
Chromatiaceae/metabolismo , Cilióforos/metabolismo , Cadena Alimentaria , Agua Dulce/microbiología , Oxígeno/farmacología , Zooplancton/metabolismo , Anaerobiosis , Animales , Bacterioclorofila A/metabolismo , Biomasa , Brasil , Ecosistema , Agua Dulce/química , Oxígeno/metabolismo , Consumo de Oxígeno , Fotosíntesis , Estaciones del AñoRESUMEN
Two strains of a novel aerobic, bacteriochlorophyll a-containing species of the alpha-4 subclass of the Proteobacteria were isolated from the hot spring at Alcafache in central Portugal. 16S rRNA gene sequence-based phylogenetic analyses showed the two novel isolates to be phylogenetically related to members of the genera Erythrobacter, Erythromicrobium and Porphyrobacter. The strains produce reddish-orange-pigmented colonies, have an optimum growth temperature of about 50 degrees C and could be distinguished from the species Porphyrobacter tepidarius, which also has a high growth temperature, primarily on the basis of the fatty acid composition. The novel species does not grow anaerobically in the presence or absence of a light source. The strains of the novel species utilize several single carbon sources for growth, most of which are also used by P. tepidarius. The species status of strains ALC-2T and ALC-3 was confirmed by low reassociation values of the DNA with species of the genera Erythrobacter, Erythromicrobium and Porphyrobacter. Phenotypic characteristics and 16S rRNA gene sequence analyses also show that strains ALC-2T (=DSM 12079T =ATCC BAA-386T) and ALC-3 (=DSM 12080) represent a novel species, for which the name Porphyrobacter cryptus sp. nov. is proposed.