The effects of heavy metals on the feeding rate of Euplotes mutabilis (Tuffrau, 1960)

Transcriptional profiling of antioxidant defense system and heat shock protein (Hsp) families in the cadmium- and copper-exposed marine ciliate Euplotes crassu

To understand the transcriptional response of antioxidant defense system and heat shock protein (Hsp) families of the marine ciliate Euplotes crassus, we analyzed the transcriptome profile using RNA-seq technology after exposure to cadmium (Cd) and copper (Cu). De novo sequence assembly produced 61,240 unigenes with 21,330 BLAST hits and showed high sequence orthology with transcriptomes of other ciliates. Gene annotation and gene ontology (GO) comparison revealed that E. crassus expressed highly diversified but conserved stress-responsive gene families of the antioxidant defense system and Hsps. After waterborne exposure to 250 μg/L of Cd and 25 μg/L of Cu, transcriptional responses of the gene families were significantly modulated, suggesting that even the unicellular E. crassus has a conserved molecular defense mechanism, such as modulating mRNA expression, for homeostasis. These transcriptional responses make E. crassus a potential model for understanding the molecular response of single cell ciliates to heavy metal contamination.

Colonisation and succession of marine biofilm-dwelling ciliate assemblages on biocidal antifouling and fouling-release coatings in temperate Australia

Ciliate assemblages are often overlooked, but ubiquitous components of microbial biofilms which require a better understanding. Ciliate, diatom and bacterial colonisation were evaluated on two fouling-release (FR) coatings, viz. Intersleek 970 and Hempasil X3, and two biocidal antifouling (AF) coatings, viz. Intersmooth 360 and Interspeed 5640, in Port Phillip Bay, Australia. A total of 15 genera were identified during the 10 week deployment. Intersleek 970 displayed the most rapid fouling by ciliates, reaching 63.3(± 5.9) cells cm(-2). After 10 weeks, all four coatings were extensively fouled. However, the toxicity of the AF coatings still significantly inhibited microbial fouling compared to the FR coatings. On all treatments, colonies of sessile peritrichs dominated the ciliate assemblage in the early stage of succession, but as the biofilm matured, vagile ciliates exerted more influence on the assemblage structure. The AF coatings showed selective toxic effects, causing significant differences in the ciliate species assemblages among the treatments.

Acute toxicity of heavy metals towards freshwater ciliated protists

The acute toxicity of five heavy metals to four species of freshwater ciliates (Colpidium colpoda, Dexiotricha granulosa, Euplotes aediculatus, and Halteria grandinella) was examined in laboratory tests. After exposing the ciliates to soluble compound of cadmium, copper, chromium, lead, and nickel at several selected concentrations, the mortality rate was registered and the LC50 values (with 95% confidence intervals) were calculated. Large differences appeared in sensitivities of the four species to the metals. H. grandinella showed the highest sensitivity for cadmium (0.07 mg l(-1), LC50) and lead (0.12 mg l(-1), LC50), whilst E. aediculatus showed the highest sensitivity for nickel (0.03 mg l(-1), LC50). The comparison with data obtained with other species indicate that Halteria grandinella and Euplotes aediculatus are excellent and convenient bioindicator for evaluating the toxicity of waters and wastewaters polluted by heavy metals. The short time (24 h) and simplicity of the test procedure enable this test to be used in laboratory studies.

Toxicity and bioaccumulation of lead and cadmium in marine protozoan communities

The behavior of lead and cadmium in a protozoan community was studied in order to obtain new data regarding the toxicity and bioaccumulation of these heavy metals. For this purpose, microcosms with different concentrations of the pollutants (without metals, 500 microg Cd and Pb x L(-1) 1,000 microg Cd and Pb x L(-1)) were used. Protozoans bioaccumulated 7.03-207.00 microg Pb x g(-1) dry weight (dw) and 0.05-332.75 microg Cd x g(-1) dw, representing an accumulation capacity of up to 161.45 microg Pb x g(-1) dw and 310.75 microg Cd x g(-1) dw more than that of the bacteria. The addition of both metals caused a significant reduction in the density of protozoans. These data were compared with those obtained previously in treatments that used these metals separately.

The acute toxicity of nickel to freshwater ciliates

The acute toxicity of nickel to 12 species of freshwater ciliates was examined in laboratory tests. After exposing standard cultures of the ciliates to a soluble compound of nickel (NiCl(2).6H(2)O) at several selected concentrations close to the lethal limit for 24 h, the mortality rate was registered and the LC(50) values (with 95% confidence intervals) were calculated. Large differences appeared in sensitivities of the 12 species to the metal. Ciliated protozoa such as Spirostomum teres (0.17 mg Ni l(-1), 24-h LC(50)) and Paramecium bursaria (0.36 mg Ni l(-1), 24-h LC(50)) showed the highest sensitivity to the nickel, while Euplotes patella (7.7 mg Ni l(-1), 24-h LC(50)) was the most tolerant species. A comparison of these results with data obtained for other heavy metals indicates that S. teres is an excellent and convenient bioindicator for evaluating the toxicity of waters polluted by heavy metals.

Toxicity and bioaccumulation of lead in marine protozoa communities

The toxicity and bioaccumulation of lead has been studied using marine protozoa communities developed in laboratory microecosystems. The concentrations tested were 500 and 1000 micrograms.L-1 of lead as lead acetate. The protozoan was able to bioaccumulate 27.02-504 micrograms Pb.g-1 dry weight. Bacteria also bioaccumulated lead, but always to a lesser degree than protozoa. Lead caused a significant reduction in the density of protozoa, which could be an indirect response to the cellular increase of lead. On the other hand, the toxicant did not determine a decrease in the number of bacterial cells; this could be due to their capacity to bioaccumulate a lesser amount of lead, the increase in the number of dead cells, and the elimination of their predators by the toxicant. After 120 h, a recovery of the community was observed.