Protozoan Taxa Research Articles

The Current State and Future Potential of Microbial Control of Scarab Pests

Injury and control costs for the invasive scarab Japanese beetle (Family Scarabeidae, Popillla japonica) alone is estimated at $450 million per year in the U.S. Chemical controls are commonly used to control scarab pests, but concerns about human safety and negative impacts on beneficial and non-target organisms, such as pollinators, are increasingly driving the market towards less toxic and more environmentally friendly management options. Microbial entomopathogens are excellent candidates for biopesticides and biocontrol agents. Although microbial pesticides currently make up only 1–2% of the insecticide market, the discovery and development of new microbes are increasing. Microbial products are non-toxic to humans and most are species-specific, reducing non-target effects. While some are slow-acting, others provide rapid control and some can be as efficacious as chemical insecticides, particularly when used in combination. Another major advantage of microbial controls is that many can persist in the environment, and become biocontrol agents, providing long-term control and reducing costs. This article provides a summary of the microbial entomopathogens that are known to infect scarab beetle species including bacterial, fungal, viral, microsporidian, and protozoan taxa, as well as the existing formulations and their efficacy. Lesser-known microbial species are also discussed as potential future controls. We also discuss the development of new techniques for improving efficacy, such as genetic engineering, synergistic interactions, auto-dissemination strategies, and improved formulations.

Metabarcoding of bacteria and parasites in the gut of Apodemus agrarius

BackgroundThe striped field mouse Apodemus agrarius is a wild rodent commonly found in fields in Korea. It is a known carrier of various pathogens. Amplicon-based next-generation sequencing (NGS) targeting the 16S ribosomal RNA (rRNA) gene is the most common technique used to analyze the bacterial microbiome. Although many bacterial microbiome analyses have been attempted using feces of wild animals, only a few studies have used NGS to screen for parasites. This study aimed to rapidly detect bacterial, fungal and parasitic pathogens in the guts of A. agrarius using NGS-based metabarcoding analysis.MethodsWe conducted 18S/16S rDNA-targeted high-throughput sequencing on cecal samples collected from A. agrarius (n = 48) trapped in May and October 2017. Taxa of protozoa, fungi, helminths and bacteria in the cecal content were then identified.ResultsAmong the protozoa identified, the most prevalent was Tritrichomonas sp., found in all of the cecal samples, followed by Monocercomonas sp. (95.8% prevalence; in 46/48 samples) and Giardia sp. (75% prevalence; in 36/48 samples). For helminths, Heligmosomoides sp. was the most common, found in 85.4% (41/48) of samples, followed by Hymenolepis sp. (10.4%; 5/48) and Syphacia sp. (25%; 12/48). The 16S rRNA gene analysis showed that the microbial composition of the cecal samples changed by season (P = 0.005), with the linear discriminant analysis effect size showing that in the spring Escherichia coli and Lactobacillus murinus were more abundant and Helicobacter rodentium was less abundant. Helicobacter japonicus was more abundant and Prevotella_uc was less abundant in males. The microbial composition changed based on the Heligmosomoides sp. infection status (P = 0.019); specifically, Lactobacillus gasseri and Lactobacillus intestinalis were more abundant in the Heligmosomoides sp.-positive group than in the Heligmosomoides sp.-negative group.ConclusionsThis study demonstrated that bacterial abundance changed based on the season and specific parasitic infection status of the trapped mice. These results highlight the advantages of NGS technology in monitoring zoonotic disease reservoirs.Graphical

PARASITES OF THE BRAZILIAN ROCK CAVY, KERODON RUPESTRIS: REVEALING THEIR HISTORY IN THE BRAZILIAN SEMIARID REGION.

Using microscopy and/or immunodiagnosis, the authors analyzed 284 fecal samples from the Brazilian rock cavy, Kerodon rupestris, that were collected between 1984 and 2015 in Serra da Capivara National Park for the presence of helminths and protozoa. Fourteen morphospecies of helminth eggs of the following taxa were found: Trematoda, Nematoda, Strongylidae, Lagochilascaris sp., Strongylida, Trichuris (2 species), Oxyuridae (3 species), Ancylostomatidae (2 species), and Ascarididae (2 species), along with 3 protozoan taxa: Coccidia, Cryptosporidium sp., and Balantidium sp. During the last 30 yr, the population of K. rupestris has increased in the region as a consequence of the creation and management of the National Park, and data from this study show a concurrent increase in the diversity of intestinal parasites in this host, including new reports. Some of these species have zoonotic potential, which suggests that K. rupestris may be in contact with domestic farm animals and/or human feces. These results show the importance of integrating different diagnostic approaches for the identification of protozoa in the region and indicate that further methods need to be employed to increase recovery. This work highlights the usefulness of parasite studies in assessing the health of ecosystems, especially in protected areas, which should be considered by park managers and health agencies.

Ecological Studies of Barwala Link Canal in Narwana Region, Haryana

The present paper deals with the monthly variations in physico-chemical characteristics and planktonic diversity of Barwala Link Canal which link the Bhakra Main Canal with Sirsa Branch of Western Yamuna Canal in Narwana Region, Haryana. Surface water samples were collected on monthly basis and analyzed for physico-chemical parameters (water temperature, total dissolved solids, electrical conductivity, turbidity, pH, dissolved oxygen, free CO2, alkalinity, hardness, chlorides, biochemical oxygen demand, o-phosphate, nitrate and ammonia). An attempt was also made to assess the biological parameters including population density, their abundance and species diversity index of plankton life which were used as a measure of water quality. Phytoplankton was abundant as compared to Zooplankton. A total of 14 taxa of phytoplankton were recorded of which 9 taxa of Chlorophyceae and 5 taxa of Bacillariophyceae. 8 taxa of zooplankton were recorded of which 4 taxa of protozoa, 3 taxa of rotifera and one taxa of insecta. Shannon diversity index of phytoplankton ranges from 2.47 to 3.29 and Zooplankton ranges from 2.60 to 2.99. It is revealed that the quality of canal water is good throughout study period as estimated by the weighted arithmetic index method.

Ecological water quality assessment in the Guapiaçu-Macacu hydrographic complex (Rio de Janeiro, Brazil) using multiple indicators

A quick diagnosis of the ecological quality of five sections of the Macacu-Guapiacu hydrographic complex was performed using visual assessment protocol (VAP), conventional analysis, composition and structure of ciliates and the occurrence of benthic macro invertebrates. Water samples were collected from five sampling stations (A-E) in July of 2010. Protists were sampled with aid of artificial substrates, and macro invertebrates were sampled using the multi-habitat method. A total of 22 taxa of protozoa and 51 taxa of macro invertebrates was registered at the five stations. Reference station (A) showed greater protist diversity and higher values of BMWP-CETEC and IBE-IOC indices relating to macro invertebrates. The impacted stations (B and E) presented lower diversity and higher abundance of protozoa, as well as the lowest values for the rates. The four methods used were convergent to diagnose reference station (A), the impacted stations (B and E) and those in intermediate conditions (C and D). Thus, the methods were complementary, as the conventional parameters and ciliate assembly were more sensitive to detecting the increase in organic pollution and VAP and macro invertebrate assembly detected changes in geomorphology and habitat degradation.

Protozoa and Oxygen

Aerobic protozoa can maintain fully aerobic metabolic rates even at very low O 2 -tensions; this is related to their small sizes. Many - or perhaps all - protozoa show particular preferences for a given range of O 2 -tensions. The reasons for this and the role for their distribution in nature are discussed and examples of protozoan biota in O 2 -gradients in aquatic systems are presented. Facultative anaerobes capable of both aerobic and anaerobic growth are probably common within several protozoan taxa. It is concluded that further progress in this area is contingent on physiological studies of phenotypes.

A simplified experimental model for clearance of some pathogenic bacteria using common bacterivorous ciliated spp. in Tigris river

Bacteria-specific uptake rates of three different protozoan taxa on a pure and mixed bacterial community was studied by means of a simplified and functionally reproducible experimental model. The bacterial species Shigella flexneri, Escherichia coli and Salmonella typhi were isolated and classified from stool samples of patients suffering from diarrhea. Paramecium caudatum, Tetrahymena pyriformis and Halteria grandinella, free living ciliate Protozoans, were isolated and identified from Tigris river water. Pure and mixed (E. coli + S. typhi), (E. coli + Sh. flexneri) bacterial cultures were used with each ciliate genera to evaluate the following: predator duplication rate, prey reduction rate, clearance rate and net grazing rate. We used selective lactose fermentation phenomena of enteric bacteria on MacConkey medium for the quantification of bacteria cultural characteristics. The final bacteria concentration was reduced by growing protozoa of 98–99.9 % compared to protozoa-free controls. It showed that Tetrahymena pyriformis had the highest duplication rate (4.13 time/day) in both types of cultures (pure and mixed), followed by Paramecium caudatum and Halteria grandinella, respectively. Paramecium caudatum had the highest rate of ingestion in both types of cultures (26 × 103 bacteria/organism/hr) and yielded the longest time required for 90 % bacterial reduction in a pure suspension of S. typhi (166 h). Clearance rates of pathogenic bacteria by ciliates ranged between 106 nanoliter/organism/h by P. caudatum to S. typhi and 1.92 nanoliter/organism/h seen in T. pyriformis in (E. coli + S. typhi) mixed culture. We used aquatic experimental microcosms under controlled conditions to explore bacteria-dependent ciliate growth and examined whether these ciliates could discriminate between equally sized bacterial preys in a mixture.

Occurrence of organic chlorinated pesticides and their ecological effects on soil protozoa in the agricultural soils of North Western Beijing, China

The occurrence of ∑HCHs, ∑DDTs, protozoa abundance and their community structure in surface soils of orchards, vegetable lands, and barren lands in northern west outskirts of Beijing were detected in order to investigate the protozoa responses to low dose organic chlorinated Pesticides (OCPs) after long-term field-based exposure. Significant differences in total concentrations of HCHs and DDTs were found among the three general groups ranking in decreasing order of concentration from orchard>vegetable lands >barren lands. Ciliate was the rare group in surface soils of all the sampling groups. The abundance of flagellate, ciliate, and amoebae in vegetable soils were significantly higher than those in orchard soils. The abundance of all the taxa of protozoa was strongly negative correlated with the residue level of ∑HCHs and ∑DDTs (P<0.05) in agricultural soils. However, no negative correlation between the residue levels of OCPs and protozoa abundance was shown in both the orchard and the barren soils. This field study demonstrated a considerable long-term impact of the OCPs residue on the abundance of protozoa in soils, and that the abundance of soil protozoa was much more influenced by land use type in association with different soil properties.

Checklist dos "protozoários" de água doce do Estado de São Paulo, Brasil

Listagens de espécies são importantes para o conhecimento da biota de um local, sua ecologia e para podermos dimensionar sua exploração econômica, biotecnológica e conservação. Neste trabalho foram levantados os dados de protozoários (ciliados, amebas nuas, amebas com carapaça, heliozoários e flagelados heterotróficos) de água doce do Estado de São Paulo. De 75 ambientes que foram analisados até o momento, foram registrados um total de 471 diferentes taxa de protozoários distribuídos em 218 generos e 304 espécies. Dos grupos de protozoários avaliados, os mais bem representados foram os ciliados com 160 gêneros e 219 espécies. Dentre os ciliados ocorrerem dois novos registros: Neobursaridium gigas Balech, 1941 para o Brasil e Loxodes rex Dragesco, 1970 para a América do Sul.

Mite dispersal among the Southern Ocean Islands and Antarctica before the last glacial maximum

It has long been maintained that the majority of terrestrial Antarctic species are relatively recent, post last glacial maximum, arrivals with perhaps a few microbial or protozoan taxa being substantially older. Recent studies have questioned this 'recolonization hypothesis', though the range of taxa examined has been limited. Here, we present the first large-scale study for mites, one of two dominant terrestrial arthropod groups in the region. Specifically, we provide a broad-scale molecular phylogeny of a biologically significant group of ameronothroid mites from across the maritime and sub-Antarctic regions. Applying different dating approaches, we show that divergences among the ameronothroid mite genera Podacarus, Alaskozetes and Halozetes significantly predate the Pleistocene and provide evidence of independent dispersals across the Antarctic Polar Front. Our data add to a growing body of evidence demonstrating that many taxa have survived glaciation of the Antarctic continent and the sub-Antarctic islands. Moreover, they also provide evidence of a relatively uncommon trend of dispersals from islands to continental mainlands. Within the ameronothroid mites, two distinct clades with specific habitat preferences (marine intertidal versus terrestrial/supralittoral) exist, supporting a model of within-habitat speciation rather than colonization from marine refugia to terrestrial habitats. The present results provide additional impetus for a search for terrestrial refugia in an area previously thought to have lacked ice-free ground during glacial maxima.

Top-down and bottom-up effects of a processing detritivore

Detritus processing, the breaking down of organic matter into smaller particles, is an essential operation in aquatic systems because it provides resources to filter feeders and accelerates nutrient release by microorganisms. Detrital foodweb dynamics are influenced by both consumption (top-down) and production (bottom-up) effects. We tested the effects of predators and detritivores on the abundance of microorganisms in an inquiline community in pitcher plants. We manipulated densities of mosquitoes (top predator) and midges (processing detritivore) in a factorial press experiment and measured the response (density) of bacteria, protozoa, and rotifer populations over several generations. We hypothesized that: 1) midges would have a positive effect on microorganisms by increasing nutrient availability (bottom-up effects), 2) mosquitoes would depress microorganism populations through consumption (top-down effects), 3) top-down and bottom-up effects would operate independently, and 4) would attenuate with trophic position. Mosquitoes (predators) had a negative effect on all measured populations. Midges (processing detritivores) had a positive effect on bacteria, but a negative effect on rotifers and some protozoan taxa. The increase in bacterial density probably was the result of nutrient enrichment from detritus processing, whereas the decrease in rotifers seems to have been the result of consumption by midges. Our study shows that the role of processing detritivores is complex and can enhance both bottom-up and top-down effects. Specifically, omnivory can complicate simple top-down and bottom-up predictions. Although they accelerate decomposition by microorganisms and, thereby, can increase resource availability, processing detritivores can also be important consumers in detrital food webs.

Zooplankton grazing on bacteria and cyanobacteria in a eutrophic lake

During in situ experiments in a cyanobacteria- and copepod-dominated eutrophic subtropical lake, all taxa of protozoa and metazoan zooplankton grazed fluorescently labelled bacteria and all metazoan zooplankton taxa grazed large filamentous and colonial cyanobacteria.

An examination of the biodiversity–ecosystem function relationship in arable soil microbial communities

Microbial communities differing in biodiversity were established by inoculating sterile agricultural soil with serially diluted soil suspensions prepared from the parent soil. Three replicate communities of each dilution were allowed to establish an equivalent microbial biomass by incubation for 9 months at 15°C, after which the biodiversity–ecosystem function relationship was examined for a range of soil processes. Biodiversity was determined by monitoring cultivable bacterial and fungal morphotypes, directly extracted eubacterial DNA and protozoan taxa. In the context of this study biodiversity relates to the numbers and proportions of different microbial species. Biodiversity decreased by ca. 15, 40 and 60% at each successive dilution step. There was no consistent effect of biodiversity on a range of soil processes measured (incorporation of thymidine and leucine, potential nitrification, nitrate accumulation, respiratory growth response, community level physiological profile and decomposition). Neither was there a direct effect of biodiversity on the variability of the processes, nor on the stability of decomposition when the soils were perturbed by heat or copper. The biodiversity of, and inter-relationships within, the microbial communities was such that the experimental reductions had no direct effects on soil function.

Intestinal parasite burden in five troops of olive baboons (Papio cynocephalus anubis) in Gombe Stream National Park, Tanzania

A cross-sectional parasitological study of a population of wild olive baboons (Papio cynocephalus anubis), consisting of 5 troops, was conducted in Gombe Stream National Park. Baboons were individually recognizable. Information on age, sex, troop membership, reproductive status, social rank and life-history of each individual baboon could be related to parasite infection. Seven helminth taxa and 2 protozoan taxa were found. All baboons were parasitized by at least 1 taxon. Distributions of helminths were aggregated among hosts. There were significant differences among troops in the prevalence of all but 2 of the recorded helminths. Age had a significant impact on the prevalence and intensity of Strongyloides sp. No significant effect of sex on the prevalence of infection could be detected. There was some indication that female reproductive status was related to Trichuris egg output. In contrast to a previous study, no significant correlations between parasite infection and social rank could be found. Troop membership constituted the predominant factor contributing to heterogeneity of prevalence of infection. This suggests that spatial location and/or genetics may be important in determining levels of parasite infection.

Changes in epilithic communities due to individual and combined treatments of zinc and snail grazing in stream mesocosms.

Effects of 0.5 mg/liter zinc (Zn) and snail grazing (400 snails/m2) on density of dominant algal and protozoan taxa, epilithic glucose respiration, and ash-free dry weight (AFDW) were examined using established (12-day colonization) periphyton communities in flow-through stream mesocosms with four treatments (Zn, snails, Zn and snails, control) for 30 days. Grazing and Zn similarly reduced the abundance of 5 of 10 dominant algal taxa and AFDW during the first 10 days of treatment. Abundance of these taxa and AFDW in grazed (ambient Zn) treatments approached control levels after 10 days as the effect due to snails decreased. Decreasing temperatures may have reduced snail activity. Snails, Zn, and the combination of these treatments contributed to higher rates of glucose respiration per unit AFDW. Protozoan species abundance was reduced to less than half by Zn but was unaffected by snails. Although Zn and snails individually altered structural and functional aspects of this microbial community, the effects when both treatments were combined could not always be inferred from the individual effects. Testing individual and combined variables that affect periphyton with a corresponding assessment of population dynamics, biomass, and community functional attributes will enhance understanding of the overall effects of pollutants on periphyton communities.

Seasonal change of protozoa and micrometazoa in a small pond with leaf litter supply

Protozoa and micrometazoa were observed in a small pond with leaf litter over a 2 year period. The total number of taxa observed in this pond was 83 protozoans and 30 micrometazoans, and the correspondence of each taxon and the habitats of surface water, leaf litter on the pond bottom and sedimented mud was noted. The microfauna in the litter on the pond bottom had a higher diversity than in the water or the sedimented mud. Patterns of seasonal change in the density of organisms — with one or two peaks in a year — were recognized in some taxa of protozoa and micrometazoa. Most peaks of bacterivorous protozoa in the leaf litter appeared in late autumn and spring. This phenomenon is considered to be closely related to the litter decomposition, because reduction of dissolved oxygen and/ or high bacterial density were observed in these two seasons. Nineteen species of protozoa from this pond were cultured in vitro with fallen leaves. From the results of the cultures and the observation of food vacuoles of protozoa in situ, part of the food web of the microfauna in the pond was estimated.

The Charms and Rewards of the Study of Minor Protozoan Taxa*

The Charms and Rewards of the Study of Minor Protozoan Taxa*