Characterization of a Deep‐Branching Heterolobosean,Pharyngomonas turkanaensis n. sp., Isolated from a Non‐Hypersaline Habitat,and Ultrastructural Comparison of Cysts and Amoebae Among Pharyngomonas Strains

An unusual heterolobosean amoeba, isolate LO, was isolated recently from a sample with a salinity of ~4‰, from Lake Turkana in East Africa. 18S rDNA phylogenies confirm that isolate LO branches among halophilic amoeboflagellates assigned to Pharyngomonas. We examined the ultrastructure of the amoeba and cyst stages of isolate LO, as well as the amoebae and cysts of Pharyngomonas kirbyi (isolates AS12B and SD1A). The amoebae of all three isolates lacked discrete dictyosomes and had discoidal/flattened mitochondrial cristae, but the mitochondria were not enrobed by rough endoplasmic reticulum. The cysts of all three isolates showed a thick, bipartite cyst wall, and lacked cyst pores. The cysts of isolate LO were distinct in that the ectocyst was very loose‐fitting, and could contain “crypts”. No flagellate form of isolate LO has been observed to date, and a salinity‐for‐growth experiment showed that isolate LO can grow at 15–100‰ salinity, indicating that it is halotolerant. By contrast, other studied Pharyngomonas isolates are amoeboflagellates and true halophiles. Therefore, we propose isolate LO as a new species, Pharyngomonas turkanaensis n. sp. It is possible that P. turkanaensis descended from halophilic ancestors, and represents a secondary reestablishment of a physiology adapted for moderate salinity.     

Parameters of fermentation and rumen microbiota of Nellore steers fed with different proportions of concentrate in fresh sugarcane containing diets

The objective of this study was to evaluate the effect of a fresh sugarcane-based diet and different roughage-to-concentrate ratios (70:30, 60:40, 40:60 and 20:80) on the rumen microbiota associated with rumen fermentation parameters and the intake and apparent digestibility of nutrients in Nellore steers. Eight rumen-cannulated Nellore steers (331 ± 8 kg BW) were distributed in a double 4 × 4 Latin square design balanced for the control of the residual effect. The ruminal pH decreased (p < 0.01) and the concentrations of N–NH₃, isovaleric and valeric acids increased linearly (p < 0.05) with an increase dietary concentrate level. Furthermore, an increased concentrate proportion reduced the population of Fibrobacter succinogenes and Ruminococus flavefaciens (p < 0.01) and increased the population of Selenomonas ruminantium and Megasphaera elsdenii (p < 0.01). The protozoa count revealed a predominance of the genus Entodinium. The synthesis of microbial N [g/d] and the efficiency of microbial synthesis [g of microbial N/kg of organic matter apparently digested in the rumen] increased as the proportion of concentrate was increased (p < 0.05). Therefore, it can be concluded that an increasing proportion of concentrate in sugarcane-containing diets enhances the synthesis of microbial protein and does not alter the fibre digestibility, although the population of fibre fermenting bacteria was reduced.     

The effect of rumen ciliates on chitinolytic activity,chitin content and the number of fungal zoospores in the rumen fluid of sheep

The objective of this study was to investigate the effect of selected protozoa on the degradation and concentration of chitin and the numbers of fungal zoospores in the rumen fluid of sheep. Three adult ewes were fed a hay-concentrate diet, defaunated, then monofaunated with Entodinium caudatum or Diploplastron affine alone and refaunated with natural rumen fauna. The average density of the protozoa population varied from 6.1 · 10⁴ (D. affine) to 42.2 · 10⁴ cells/ml rumen fluid (natural rumen fauna). The inoculation of protozoa in the rumen of defaunated sheep increased the total activity of chitinolytic enzymes from 2.9 to 3.6 μmol N-acetylglucosamine/g dry matter (DM) of rumen fluid per min, the chitin concentration from 6.3 to 7.2 mg/g DM of rumen fluid and the number of fungal zoospores from 8.1 to 10.9 · 10⁵ cells/ml rumen fluid. All examined indices showed diurnal variations. Ciliate population density was highest immediately prior to feeding and lowest at 4 h thereafter. The opposite effects were observed for the numbers of fungal zoospores, the chitin concentration and chitinolytic activity. Furthermore, it was found that chitin from zoospores may account for up to 95% of total microbial chitin in the rumen fluid of sheep. In summary, the examined ciliate species showed the ability of chitin degradation as well as a positive influence on the development of the ruminal fungal population.     

Variations in the activity of fatty ACYL-CoA desaturases and electron-transport components in Tetrahymena microsomes with temperature and age of culture

1. 1.|Alterations in the fatty acid composition of microsomes were most marked in the exponential phase of both 39.5- or 15°C- grown Tetrahymena pyriformis NT-1.

2. 2.|Activities of palmitoyl-CoA and stearoyl-CoA desaturases were lower in 15°C cells than in 39.5°C cells, while the activity of oleoyl-CoA desaturase was higher in 15°C cells.

3. 3.|Activities of the terminal component of the desaturation system as well as all three desaturases (palmitoyl-CoA, stearoyl-CoA, oleoyl-CoA) were higher in the exponential phase than in the stationary phase for cells grown at both temperatures.

4. 4.|NAD(P)H-cytochrome c reductase activity and cytochrome b₅ content were reduced whereas NADH-ferricyanide reductase activity was increased in the stationary phase at both 39.5 and 15°C.

The ecology of two species of primitive ciliated protozoa commonly found in standing freshwaters (Loxodes magnus stokes and L. striatus penard)

The distribution of Loxodes magnus and L. striatus (Karyorelictida) was investigated in two eutrophic waters (Esthwaite Water and Priest Pot, English Lake District). In the benthos, these species were most abundant at the sediment surface, at deeper sites, and when the bottom water was oxygenated. In the plankton, in Priest Pot, they were found only in the oxygen deficient summer hypolimnion. Experimental studies suggested that L. magnus and L. striatus required access to oxygen. Loxodes was apparently excluded from the oxygenated Priest Pot epilimnion by several adverse factors, one of which was bright light. It was concluded that the ecology of L. magnus and L. striatus resembles, in many ways, that of the advanced ciliates which were found associated with Loxodes.     

Plasmodium berghei: Effect of carrageenan on the course of infection in the A/J mouse

Seakem-9 calcium carrageenan, a reported anti-macrophage agent, was found to confer partial immunity in mice subsequently challenged with 5 × 10⁵Plasmodium berghei NK65A parasitized erythrocytes. Transient parasitemias and significantly extended survival times were evident in carrageenantreated animals. It was suggested that carrageenan may have enhanced nonspecific cellular immunological mechanisms or affected specific immune reactions through the cytotoxicity to suppressor macrophages.     

Minchinia teredinis N. Sp. (Balanosporida, Haplosporidiidae), a Parasite of Teredinid Shipworms

ABSTRACT. A new species of ascetosporan parasitizing tissues of woodboring mollusks of the genus Teredo , including T. navalis Linnaeus, T. furcifera von Martens, and T. bartschi Clapp, is described from light and transmission electron microscopical observations. The new species is assigned the name Minchinia teredinis sp. n. (Phylum Ascetospora, Class Stellatosporea, Order Balanosporida, Family Haplosporidiidae). Plasmodia, sporonts, sporocysts, and mature spores are found in all host tissues, but primarily in the gill. Spores are obovate, operculate, and characterized by four projections from the epispore membrane. The species is found from Long Island Sound to Virginia on the east coast of the United States. The parasite causes extensive damage to host tissues and is correlated with reductions in host populations.     

Growth studies on xenic cultures of Entamoeba gingivalis using established media

Wantland's egg medium, modified Shaffer-Frye (MSF) medium and Tryptose-Trypticase-Yeast Extract-Serum-Blood (TTY-SB) medium were compared with variations of the latter two media for their ability to support xenic growth of Entamoeba gingivalis. Wantland's egg medium was unsuitable for growth of E. gingivalis. Accompanying bacteria became resistant to penicillin and streptomycin, overwhelming the amoeba culture. MSF medium was also unsuitable for the cultivation of E. gingivalis. Bacterial growth was heavy and protozoan growth sparse. MSF medium without mercaptosuccinic acid, but with rice starch, dextran or levan substituted for glucose and with Yersinia enterocolitica added, supported limited growth of the amoeba. Unmodified TTY-SB medium did not sustain growth of E. gingivalis. However, when rice starch suspension was substituted for glucose, -cysteine HCl was deleted, and a Crithidia sp. was added to the E. gingivalis culture grown xenically, enhanced growth of the oral amoeba resulted in this modified TTY-SB medium. E. gingivalis is very sensitive to changes in incubation temperature. Optimum growth was found to be in the narrow range from 34.5 to 35°C for all media tested.     

Increase in activity and biosynthesis of phospholipase A of Entamoeba histolytica by cholesterol passage

Phospholipase A (EC 3.1.1.4) activity was detected in trophozoites and cell-free culture medium of Entamoeba histolytica NIH-200. The enzyme from both the sources gave two pH optima at 4.2 and 9.0 and was stimulated by addition of CaCl₂. Cholesterol passage of the amoeba increased the enzyme activity and trophozoite-multiplication. The enzyme was purified by submitting the trophozoites to freezing and thawing, treatment with triton X-100, heat denaturation, and chromatography on Sephadex G-100. The purified enzyme resolved on sodium dodecyl sulphate gel electrophoresis into two protein bands, one exhibiting optimal phospholipase A activity at pH 4.2 and the other at pH 9.0. Incorporation of ¹⁴C ammo acids into the proteins at various stages of enzyme purification suggests that cholesterol passage increased the synthesis and activity of phospholipase A in the trophozoites.     

Effects of different molecular weight fractions of dissolved organic matter on the growth of bacteria,algae and protozoa from a highly humic lake

Effects of different molecular size fractions (< 1000 MW, < 10 000 MW, < 100 000 MW and <0.1 μm) of dissolved organic matter (DOM) on the growth of bacteria, algae and protozoa from a highly humic lake were investigated. DOM from catchment drainage water as well as from the lake consisted mostly (59–63%) of high molecular weight (HMW) compounds (> 10 000 MW). With excess inorganic nutrients, the growth rate and yield of bacteria were almost identical in all size fractions. However, in < 1000 MW fractions and with glucose added, a longer lag phase occurred. Without added nutrients both the growth rates and biomasses of bacteria decreased towards the smaller size fractions and the percentage of dissolved organic carbon (DOC) used during the experiment and the growth efficiency of bacteria were lower than with excess nutrients. The growth efficiency of bacteria was estimated to vary between 3–66% in different MW fractions, largely depending on the nutrient concentrations, but the highest growth efficiencies were observed in HMW fractions and with glucose. The growth of algae was clearly lowest in the < 1000 MW fraction. In dim light no net growth of algae could be found. In contrast, added nutrients substantially enhanced algal growth and in deionized water with glucose, algae achieved almost the same growth rate and biomass as in higher MW fractions of DOM. The results suggested that bacteria and some algae were favoured by DOM, but protozoans seemed to benefit only indirectly, through bacterial grazing. The utilization of DOM by bacteria and algae was strongly affected by the availability of phosphorus and nitrogen.