Janusz Fyda

The use of rotifers for limiting filamentous bacteria Type 021N, a bacteria causing activated sludge bulking

The excessive growth of filamentous bacteria and the resultant bulking of activated sludge constitute a serious problem in numerous wastewater treatment plants. Lecane inermis rotifers were previously shown to be capable of reducing the abundance of Microthrix parvicella and Nostocoida limicola in activated sludge. In the present study, the effectiveness of four Lecane clones in reducing the abundance of Type 021N filamentous bacteria was investigated. Three independent experiments were carried out on activated sludge from three different treatment plants. We found that Lecane rotifers are efficient consumers of Type 021N filaments.

Predator-induced morphological changes in the ciliate Colpidium (Protozoa, Ciliophora)

Summary Of three tested species of common and well known ciliates, Colpidium kleini and C. colpoda underwent morphological transformation and significantly changed their morphology in the presence of the predacious ciliate Lembadion bullinum. C. campylum , the smallest tested prey species, did not change. The predator-induced phenotype was significantly broader than the normal one and had an almost spherical shape, as illustrated by the cell width/length ratio, ranging from 0.34 to 0.39 for typical C. kleini and 0.84 to 0.89 for the induced phenotype, depending on the clone. For the two tested clones of C. colpoda the values were 0.48 and 0.52 for the typical form and 0.77 for both transformed phenotypes. Because the total number of somatic kineties in transformed cells did not change, the distance between them almost doubled. Unlike the typical phenotype, kinetosomes in kineties of the induced phenotype were situated very near one another and their total number was significantly higher.

An investigation of predator‐induced defence responses in ciliated protozoa

Predator‐induced defence responses have been reported in 15 species of ciliates representing three subclasses: Hypotrichia, Stichotrichia and Hymenostomia. However, the discovery of this phenomenon in such distantly related groups suggests that it could be more widespread within the Ciliophora. In laboratory experiments, we tested 23 potential prey species with a range of potential predators including other ciliates (12 spp.), amoebae (two spp.), rotifers (two spp.), a turbellarian worm (Stenostomum sphagnetorum), and an oligochaete worm (Chaetogaster sp.). In each experiment, one predator species was incubated for 24 h with one potential prey species and the latter was examined for evidence of a defence response. One new example of predator‐induced morphological change was recorded (Euplotes viridis) and detailed observations were made for one poorly known example (E. eurystomus). Both species significantly increased their width (by about 35% and 23%, respectively) in the presence of the turbellarian worm S. sphagnetorum. An induced life cycle change was recorded for the first time among hypotrichs with E. muscorum exhibiting significantly increased rates of encystation in the presence of the ciliate predators Dileptus anser and Spathidium sp. Finally, Euplotes patella, Euplotes sp. and Stylonychia pustulata, which are usually regarded as omnivorous rather than predatory ciliates, all induced morphological change in Colpidium kleini, the C. kleini cells becoming significantly shorter and wider. No examples of induced defence response were found among groups other than hypotrichs and hymenostomes.

The morphology of the poorly-known freshwater urostylid ciliate Neokeronopsis spectabilis (Kahl, 1932) nov. gen. nov. comb., (Ciliophora: Urostylidae), with notes on its morphogenesis

Neokeronopsis spectabilis (Kahl, 1932) nov. gen. nov. comb. (formerly Holosticha ( Keronopsis) spectabilis ), a large, freshwater urostylid ciliate, is redescribed following examination of protargol stained material. Its morphology is characterized by: flexible cortex; large size (368–500 μm long); large buccal field and long adoral zone of membranelles which curves across the apical cell margin to the right hand side of the body; two rows of frontal cirri each forming a bicorona; long midventral row of cirri arranged in pairs; one marginal cirral row on each side of the cell; a long row of well developed transverse cirri; 6–9 caudal cirri arranged in three rows, 2–3 cirri per row; 9–12 dorsal kineties; two ovoid macronuclear nodules. Morphogenetic events in N. spectabilis are characterized by the following: (1) the parental adoral zone of membranelles (AZM) is retained in the proter while in the opisthe the AZM is formed de novo from the oral primordium; (2) the undulating membrane anlage gives rise to the paroral and endoral membranes and to the anteriormost frontal cirrus; (3) the cirral anlagen form to right of the buccal field and give rise to the frontoterminal, midventral and transverse cirri; (4) the marginal row anlagen are formed within the old structures; (5) the dorsal anlagen form in two groups; Group 1 initially comprises 3 kineties which are formed within the 3 leftmost kineties of the parental structure, although the rightmost of these proliferates to form ca. 6–8 kineties; Group 2 comprises 5 kineties which form de novo near the anterior end of the right marginal row; (6) the caudal cirri are formed at the posterior end of the rightmost and the two leftmost kineties of the Group 1 dorsal anlagen; (7) the macronuclear nodules fuse to form a single mass which divides twice prior to the separation of the daughter cells. The new genus Neokeronopsis is established on the basis of this unique combination of morphological and morphogenetic characters. The generic diagnosis is as follows: urostylid with two arched rows of frontal cirri each forming a bicorona; long midventral row of paired cirri; one marginal row on each side of the body; frontoterminal, transverse and caudal cirri present; during morphogenesis, formation of dorsal kineties is of an Oxytricha -pattern. Neokeronopsis spectabilis is fixed as the type species of the genus.

Benefits and costs of predator-induced morphological changes in the ciliate Colpidium kleini (Protozoa, Ciliophora)

Summary Phenotypic transformation of C. kleini occurred when the prey coexisted with the predatory ciliate Lembadion bullinum for at least 24 hours, and was completed after 36–48 h. Net-separated predator medium caused visible shape changes in the prey. The induced phenotype was about 60% wider and 20% shorter than the typical one and had an almost spherical shape. The results showed that the induced morphological changes are a defense against L. bullinum, which is a raptorial feeder. In the presence of 100 predators, on an average 132 of 150 induced phenotypes survived for 2 h, but in the same conditions only 33 of 150 normal phenotypes did. The predator needed significantly more time and had to repeat attacks many times to catch and engulf the morphologically transformed prey. Only 16% of the attacks ended in ingestion of the transformed prey in less than 15 min, while in 54% of the cases the typical C. kleini form was ingested during the first predator attack, which occurred in the first 2 min. The growth rate of induced C. kleini phenotypes was on an average about 25% less than that of typical ones, indicating the substantial cost of the defense mechanism. Other predacious ciliates such as Dileptus margaritifer, Homalozoon vermiculare and Stylonychia mytilus did not cause any morphological changes in C. kleini.

The Toxicity of Aluminium Salts to Lecane Inermis Rotifers: Are Chemical and Biological Methods Used to Overcome Activated Sludge Bulking Mutually Exclusive?

Abstract The aim of this study was to assess the effects of two flocculants that are often used to overcome activated sludge bulking problems - aluminium chloride, AlCl3, and aluminium sulphate, Al2(SO4)3 - on Lecaneinermis (Rotifera, Monogononta) at three different temperatures: 8, 15 and 20°C. The mean EC50 value (effective concentration, mg dm-3) calculated for the 24 h mortality test was 0.012 mg Al3+dm-3. Next, the effects of low concentrations of the Al-salts on the population development from single individuals (parthenogenetic females) were tested in a 21-day experiment. At concentrations as low as EC4.8 and EC0.48, both Al-salts affected rotifer population negatively. However, temperature was the most pronounced factor that modified the toxicity of the Al-salts to the rotifers. On the 12th day of the experiment, there were significant interactions between temperature and the Al-salts, indicating that the chemicals were more toxic to the rotifers at 20°C than at lower temperatures. The weaker rotifers sensitivity to Al-salts (especially to AlCl3) in temperatures below 15°C, when the biggest problems associated with sludge bulking occurs,may means use both rotifers and chemicals reasonable and effective. Streszczenie Sole glinu są powszechnie stosowanym fl okulantem, służącym zwalczaniu puchnięcia osadu czynnego w biologicznych oczyszczalniach ścieków. Nowa idea biologicznego zwalczania tego niekorzystnego dla prawidłowej pracy oczyszczalni zjawiska polega na zastosowaniu wrotków z gatunku z Lecaneinermis. Wrotki te naturalnie występują w osadzie czynnym i są w stanie zjadać bakterie nitkowate, jak Microthrixparvicella, sprawiające najwięcej problemów w eksploatacji oczyszczalni podczas miesięcy zimowych. Celem badań było porównanie toksyczności chlorku glinu AlCl3 oraz siarczanu glinu Al2(SO4)3 dla wrotków Lecaneinermis w trzech temperaturach: 8, 15 and 20°C. Średnią wartość EC50 (stężenie powodujące 50% efekt, mg dm-3) dla śmiertelności wrotków na podstawie 24-godzinnego testu ustalono na poziomie 0.012 mg Al3+ dm-3. Następnie, badano wpływ niskich stężeń soli glinu na tempo wzrostu populacji z pojedynczego osobnika (partenogenetyczna samica) w 21-dniowym eksperymencie. Ustalono, że stężenia na poziomie odpowiadającym EC4.8, a nawet EC0.48 wpływają negatywnie na tempo wzrostu populacji. Temperatura silnie wpływała na toksyczność glinu. W 12-tym dniu eksperymentu stwierdzono, że zachodzi istotna interakcja pomiędzy toksycznością glinu i temperaturą, wskazująca, że w 20°C glin jest bardziej toksyczny dla wrotków niż w niższych badanych temperaturach. Mniejsza wrażliwość wrotków na glin w temperaturze poniżej 15°C może oznaczać, że łączenie tych dwóch metod zwalczania puchnięcia osadu czynnego w miesiącach zimowych może być racjonalnym i efektywnym rozwiązaniem.

Effect of the rotifer Lecane inermis, a potential sludge bulking control agent, on process parameters in a laboratory-scale SBR system

The influence of a high density of rotifers, which is known to be able to control filamentous bacteria, on the parameters of an activated sludge process was examined in four professional laboratory batch reactors. These reactors allow the imitation of the work of a wastewater treatment plant with enhanced nutrient removal. The parameters, including oxygen concentration, pH and temperature, were constantly controlled. The experiment showed that Lecane rotifers are able to proliferate in cyclically anaerobic/anoxic and aerobic conditions and at dissolved oxygen concentrations as low as 1 mg/L. In 1 week, rotifer density increased fivefold, exceeding the value of 2,200 ind./mL. The grazing activity led to an improvement in settling properties. Extremely high numbers of rotifers did not affect the main parameters, chemical oxygen demand (COD), N-NH(4), N-NO(3), P-PO(4) and pH, during sewage treatment. Therefore, the use of rotifers as a tool to limit the growth of filamentous bacteria appears to be safe for the entire wastewater treatment process.

VULNERABILITY OF NOSTOC MUSCORUM AGARDH (CYANOPHYCEAE) MOTILE HORMOGONIA TO CILIATE GRAZING1

Experiments were carried out to investigate if the stage of life cycle of Nostoc muscorum Agardh alters vulnerability to grazing by Pseudomicrothorax dubius Maupas. When the percentage of motile hormogonia of all counted trichomes exceeded 10%, most of the grazers (80%–100%) became satiated within 2 h. In most cases (90%) grazers successfully attacked motile hormogonia. Attacks on nonmotile trichomes were much rarer (8%) and mainly unsuccessful. Direct observations revealed that hormogonia could be ingested by the ciliates as long as they remained motile. Hormogonia already adhered to the bottom were still recognized by ciliates as potential food but were not ingested. We did not observe attacks on old vegetative colonies. This is apparently the first report on the motile stage of Nostoc being susceptible to ciliate grazing. Experiments with other grazers, Nassula tumida Maskell and two different clones of Furgassonia blochmanni Faure‐Fremiet, showed that only one clone of F. blochmanni was able to feed on motile hormogonia, whereas the second clone and N. tumida showed no interest in them.

Lecane tenuiseta (Rotifera, Monogononta) as the best biological tool candidate selected for preventing activated sludge bulking in a cold season

AbstractRotifers in activated sludge reduce the quantity of dispersed bacteria, ingest filamentous bacteria, enhance flocculation and limit biomass production. Growth rates of rotifers are inversely correlated with temperature; thus, their density declines drastically in wastewater treatment plants (WWTPs) during the winter. The only species already demonstrated to be able to control bulking is Lecane inermis. However, they cease proliferation at 8°C. The goal of our research was to select other rotifers species whose growth rates at lower temperatures are sufficiently high to maintain a favourable density during cold seasons. We conducted selection experiments in the laboratory at temperatures reflecting the temperature distribution in the majority of municipal WWTPs in the temperate zone. In the first experiment, the general selection stage, we tested the influence of the temperatures 8, 15 and 20°C on competition among different rotifer taxa in sludge samples originating from different WWTPs. The rotif...

Effects of grazers' species identity on cyanobacteria in bitrophic and tritrophic food webs

Using laboratory microcosms, we studied direct and indirect interactions among different components of bi- and tritrophic communities. Filamentous cyanobacteria (Phormidium sp.) and autotrophic flagellates (Chlorogonium elongatum) were primary producers. The second trophic level was represented by ciliates Furgasonia blochmanni and Pseudomicrothorax dubius grazing on the filamentous cyanobacteria and two filter feeders, Euplotes octocarinatus and Stylonychia pustulata, feeding on the autotrophic flagellates. An oligochaete, Chaetogaster sp., was used as the top predator. An experiment was carried out for all combinations of two factors: (1) the identity of the cyanobacteria consumer (Furgasonia or Pseudomicrothorax) and (2) the presence or absence of the top predator. Significant effects of the treatments on both the abundance of cyanobacteria and filter feeding ciliates and predator-induced defense in Phormidium and Euplotes were observed in a 36-day experiment. The experiment showed that the substitution of one species (Furgasonia) for another (Pseudomicrothorax) seemingly playing the same ecological role may lead to significant changes in the whole community.