12 research outputs found
Factors influencing microbial mat composition, distribution and dinitrogen fixation in three western Indian Ocean coral reefs
Diatom communities on commercial biocidal fouling control coatings after one year of immersion in the marine environment
Little is known about the effect of commercial biocidal fouling control coatings on fouling diatom communities and their growth forms after long periods of exposure in the marine tropical environment. The current study investigated the abundance and composition of fouling diatom communities developed on 11 commercially available biocidal antifouling coatings, covering the three main technology types in recent historic use (Self-Polishing Copolymers, Self-Polishing Hybrid and Controlled Depletion Polymers) after one year of static immersion at two locations in Muscat, Oman (Marina Shangri La and Marina Bandar Rowdha). Light microscopy demonstrated that the total abundance of diatoms and the relative abundance of growth forms were significantly affected by the choice of biocidal antifouling coating and experimental location. Using scanning electron microscopy, a total of 21 diatom genera were identified which were grouped into adnate, motile, plocon and erect growth forms. The adnate growth forms, mainly the genera Amphora, Cocconeis and Mastogloia, dominated the other growth forms in terms of their relative abundance. Current results revealed the importance of exposure location and choice of biocidal antifouling coating on the relative abundance of diatom growth forms
Nitrogen fixation and diversity of benthic cyanobacterial mats on coral reefs in Curac¸ao
Benthic cyanobacterial mats (BCMs) have
increased in abundance on coral reefs worldwide. However,
their species diversity and role in nitrogen fixation are
poorly understood. We assessed the cyanobacterial diversity
of BCMs at four coral reef sites in Curac¸ao, Southern
Caribbean. In addition, nitrogen fixation rates of six common
mats were measured. Microscopic examinations
showed 22 cyanobacterial species, all from the order Oscillatoriales.
Species diversity was similar among sites
despite differences in overall BCM abundance. Dominant
mats were primarily composed of Hydrocoleum glutinosum,
Oscillatoria bonnemaisonii or Lyngbya majuscula.
However, some mats exhibited highly variable species
composition despite consistent macroscopic appearance.
16S rRNA-based phylogeny revealed similar species as
those identified by microscopy, with additional sequences
of unicellular (Xenococcus and Chroococcidiopsis) and
heterocystous (Rivularia and Calothrix) cyanobacteria.
Vice versa, morphotypes of Tychonema, Schizothrix and
Dichothrix were found by microscopy only. The detection
of similar species at the same sites in a study conducted
40 years ago indicates that changes in environmental
conditions over these years may have favored indigenous
species to bloom, rather than facilitated the introduction
and proliferation of invasive species. Nitrogen fixation
rates of mats were 3–10 times higher in the light than in the
dark. The highest areal nitrogen fixation rate
(169.1 mg N m-2 d-1) was recorded in the cyanobacterial
patch dominated by O. bonnemaisonii. A scale-up of
nitrogen fixation at a site with 26% BCM cover at 7 m
depth yielded an aerial rate of 13 mg N m-2 reef d-1,
which exceeds rates reported in open ocean blooms of
Trichodesmium in the Caribbean. Our results suggest that
the Caribbean basin is not only a hotspot for planktonic
nitrogen fixation, but also for benthic nitrogen fixation.
Because BCMs fix vast amounts of nitrogen, their proliferation
will strongly alter the nitrogen budget of coral
reefs
Isolation and characterization of hydrocarbon-degrading bacteria from gas station leaking-contaminated groundwater in the Southern Amazon, Brazil
Teores de β-caroteno em suplementos e biomassa de Spirulina Contents of β-carotene in supplements and biomass of Spirulina
A cianobactéria Spirulina tem sido utilizada há séculos, tendo em vista suas propriedades nutricionais e medicinais. Neste trabalho, objetivou-se analisar os teores de β-caroteno tanto em suplementos alimentares a base de Spirulina comercializados em estabelecimentos de produtos naturais no mercado varejista, quanto em S. platensis cultivada em laboratório. Alguns pigmentos carotenóides possuem atividade de vitamina A e, dentre eles, o β-caroteno é o que apresenta maior atividade biológica. A extração de β-caroteno foi feita com metanol:água (90:10 v/v), seguida de saponificação e partição em n-hexano. As análises cromatográficas foram realizadas em coluna Waters Spherisorb S5 ODS 2 (4,6 x 250 mm), usando metanol:tetrahidrofurano (90:10, v/v) bombeado a 2 mL min-1, com registro dos cromatogramas em 450 nm. Os suplementos alimentares a base de Spirulina apresentaram baixos teores de β-caroteno. A maior concentração foi encontrada em S. platensis cultivada a 24º C com fotoperÃodo de 16 h claro e 8 h escuro. Considerando sua atividade provitamÃnica, os teores de retinol equivalente (RE) nas microalgas analisadas no presente trabalho foram calculados a partir do β-caroteno para classificá-las como fonte excelente ou fonte útil de vitamina A.<br>Spirulina is a cyanobacterium that has been used for several centuries due to its nutritional and medicinal properties. This work has evaluated the contents of β-carotene both in Spirulina commercialized as food supplement, purchased from natural product shops, and in S. platensis reared under laboratory conditions. Some carotenoids exhibit pro-vitamin A activity, and β-carotene presents the greatest biological activity. β-Carotene of microalgae was extracted in 90% aqueous methanol. These extracts were saponified and partitioned in n-hexane. Chromatographic analyses were carried out in a Spherisorb column S5 ODS 2 (4.6 x 250 mm), with a mobile phase of methanol:tetrahydrofuran (90:10, v/v) delivered at 2 mL min-1 and chromatograms registered at 450 nm absorbance. Food supplement made with Spirulina presented low content of β-carotene. The highest content of β-carotene was detected in S. platensis cultivated under 24º C with photoperiod of 16 h light and 8 h dark. Considering its pro-vitamin activity, retinol equivalent (RE) was calculated from β-carotene to determine whether alga material could be claimed as an useful or an excellent source of the vitamins A
Cold-Adapted Bacterial Diversity in Mingyong Glacier based on Combination Analysis of Fatty Acids and 16S rRNA Gene Sequence
Changes in bacterial community of anthracene bioremediation in municipal solid waste composting soil*
Polycyclic aromatic hydrocarbons (PAHs) are common contaminants in a municipal solid waste (MSW) composting site. Knowledge of changes in microbial structure is useful to identify particular PAH degraders. However, the microbial community in the MSW composting soil and its change associated with prolonged exposure to PAHs and subsequent biodegradation remain largely unknown. In this study, anthracene was selected as a model compound. The bacterial community structure was investigated using terminal restriction fragment length polymorphism (TRFLP) and 16S rRNA gene clone library analysis. The two bimolecular tools revealed a large shift of bacterial community structure after anthracene amendment and subsequent biodegradation. Genera Methylophilus, Mesorhizobium, and Terrimonas had potential links to anthracene biodegradation, suggesting a consortium playing an active role