Non-living Substrates Research Articles

Copepods and diatoms: Classic examples of epibiosis along the southeastern Arabian Sea

Exoskeleton of several copepods along the coastal and offshore waters of the Southeastern Arabian Sea provide a convenient habitat for the attachment of epibiotic diatoms, Pseudohimantidium pacificum, Protoraphis sp. and Protoraphis atlantica. P. pacificum was highly host-specific towards corycaeid copepods, whereas the genus Protoraphis showed specificity towards calanoid and pontellid copepods. All the host copepods identified except Labidocera sp. formed a new host record for Protoraphis, with Scolecithrix sp. belonging to an entirely new family, Scolecitrichidae. Taxonomic description, ecological habit, biogeographic distribution, host range, attachment sites and sex preference of the diatoms are described. A high number of associations was observed in females and offshore waters, corresponding to the larger size of the host and the unavailability of non-living substrates along offshore waters. The study suggests the utilization of hosts by the diatoms as a primary habitat. The report is the first along the Arabian Sea, creating baseline data on epibiosis

Ecologising Seediq: Towards an Ecology of an Endangered Indigenous Language from Taiwan

Abstract An ecolinguistic system, like a biological ecosystem, is self-regulating, yet it cannot be entirely self-contained, because words, like living species and the non-living substrates upon which they depend, are border-crossing. As a result, any ‘language’ is to some extent ‘creolised’, lexically or syntactically. Creolisation, however, may be perceived as a threat to an endangered language. The Seediq language is endangered, and, like any language, to some extent creolised. Though much less creolised than Ilan Creole, Seediq contains numerous Japanese and Chinese loanwords. Yet many of these loanwords have Seediq analogues. It may be that the Seediq language community has responded to the influx of loanwords by coining new terms based on Seediq roots. If so, their response combines linguistic purism with cultural cosmopolitanism: the loanword is a threat, the concept is not. Regardless, the coexistence of indigenous words with loanwords is part of an ongoing linguistic adaptation to modernity. I try to understand this adaptation in terms of ‘language ecology’.

Effects of attachment substrate, larval diet, and temperature on development and survival of immature Coquillettidia linealis (Skuse) and Coquillettidia xanthogaster (Edwards).

A sustainable colony allowed investigations into attachment substrates, diet and temperature in the development of the immature stages of Cq. linealis and its local congener Cq. xanthogaster. As immatures, these mosquitoes attach to submerged plants for respiration, and various field-collected and laboratory-raised plants were compared with non-living substrates. Hydroponically-grown wheat plant seedlings provided the most suitable attachment substrate. Development and survival of immatures to eclosion were investigated with three types and three quantities of a standardized diet. Development and survival at rearing temperatures between 10° and 30° C were also investigated. Diet type appeared to have little influence on development. However, at the lowest diet quantity, development to pupation was significantly reduced while the highest diet quantity impacted on the eclosion of pupae. Mean duration of immature development for Cq. linealis increased as temperature decreased. Time from 1st instar to median eclosion did not differ significantly between 23° C (6.0 weeks) and 25° C (5.3 weeks), although it was 10 weeks at 20° C, and 30° C was lethal. For Cq. xanthogaster, similarly, mean duration of immature development increased as temperature decreased, with development time from 1st instar to median eclosion significantly longer at 20° C (7.5 weeks) compared to 23° C (5.0 weeks) and 30° C (4.0 weeks).

Using Synthetic Biology to Engineer Living Cells That Interface with Programmable Materials.

We have developed an abiotic-biotic interface that allows engineered cells to control the material properties of a functionalized surface. This system is made by creating two modules: a synthetically engineered strain of E. coli cells and a functionalized material interface. Within this paper, we detail a protocol for genetically engineering selected behaviors within a strain of E. coli using molecular cloning strategies. Once developed, this strain produces elevated levels of biotin when exposed to a chemical inducer. Additionally, we detail protocols for creating two different functionalized surfaces, each of which is able to respond to cell-synthesized biotin. Taken together, we present a methodology for creating a linked, abiotic-biotic system that allows engineered cells to control material composition and assembly on nonliving substrates.

Diatom assemblages of non-living substrates in petrifying Cratoneurion springs from lower Belgium

Diatom assemblages were examined from non-living substrates in thirteen springs supporting the Natura 2000 habitat type 'Petryfing springs with tufa formation' in the southern part of Flanders. More than 300 taxa were recorded, including some which appear to be particularly associated with this kind of environment. Even though a number of characteristic taxa and diatoms characterizing fast-flowing springs of more elevated terrain remained absent, local species richness was higher than reported from carbonate springs elsewhere in Europe. Relative abundance of 'Red List' taxa was, however, substantially lower. Taxon richness was not related to measured nutrients but increased with diatom-inferred trophic status. Assemblages consisted mainly of motile, small-celled species of Achnanthidium, Amphora, Caloneis, Planothidium and Stauroneis. Hygropetric rheocrenes presented a somewhat more distinct assemblage than helocrene and rheohelocrene settings, but overall, compositional metrics were similar among spring types. Assemblages were structured mainly along gradients of pH, major ions (in particular magnesium and potassium) and nitrate relating to calcite precipitation, aquifer and nitrogen supply. Besides substantiating broad similarities among Cratoneurion springs, the results provide arguments for a regionalized approach towards assessment of their diversity, community structure and conservation status.

Should I lay or should I wait? Egg-laying in the two-spotted spider mite Tetranychus urticae Koch

Optimality theory predicts that females tend to maximize their offspring survival by choosing the egg-laying site. In this context, the use of conspecific cues allows a more reliable assessment of the habitat quality. To test this hypothesis, Tetranychus urticae Koch is an appropriate biological model as it is a phytophagous mite living in group, protected against external aggression by a common web.Experiments were conducted to determine the respective influence of substrate (living substrate: bean leaf vs. non-living substrate: glass plate), silk and presence of conspecific eggs on the egg-laying behavior of T. urticae females.On both living and non-living substrates, the presence of silk positively influenced the probability of a female to lay an egg, but had no influence on the number of eggs deposited. The egg-laying behavior was mainly determined by the nature of the substrate with mites laying fewer eggs on a non-living substrate than on a living one. The presence of a conspecific egg had no impact on either the probability of laying an egg or on the oviposition rate.This study showed a high variability among females in their fecundity and egg-laying performance. The physiology of females (individual fecundity), the egg-laying substrate and to a lesser extent the presence of silk impacted on the decision of spider mites to lay eggs.

Attachment of the peritrich epibiont Zoothamnium intermedium Precht, 1935 (Ciliophora, Peritrichia) to artificial substrates in a natural environment

Peritrich ciliates are commonly found as epibionts, colonizing living organisms, or attached to non-living substrates in freshwater, estuarine and marine environments. Several species of peritrich epibionts are obligate, which means that they are able to only colonize other organisms, while others are facultative attaching to living or non-living substrates. The peritrich Zoothamnium intermedium is commonly found as epibiont on the copepod species Acartia tonsa and Eurytemora affinis in Chesapeake Bay, USA. Previous studies demonstrated that Z. intermedium is not able to attach to non-living substrates in the laboratory; with free-swimming stages (telotrochs) dying when living substrates are not available for colonization. The present study investigated the ability of Z. intermdium to colonize artificial substrates in the field. Observations were carried out while the peritrich ciliate was colonizing copepods in Rhode River, a tributary of Chesapeake Bay. Results demonstrated that four species of Zoothamnium were recovered from artificial substrates, but none of them was Z. intermedium. At the same time, Z. intermedium was colonizing adults and copepodites of E. affinis and A. tonsa during the whole study period. These results, in addition to laboratory observations, suggest that Z. intermedium is an obligate epibiont.

Tying new knots in synthetic biology

Recent years have seen the emergence of synthetic biology, which encompasses the engineering of living organisms as well as the implementation of biological behavior in non-living substrates. Many of these engineered systems have harnessed the diverse toolkit of proteins, genes, and cellular processes that nature offers. While these efforts have been fruitful, they have also illustrated the difficulty associated with programming highly complex functions by tapping into cellular processes. Another set of efforts has focused on building circuits, performing computation, and constructing nanoscale machines using nucleic acids. Zhang et al., 2007, Science 318, 1121-1125 and Yin et al., 2008, Nature 451, 318-322 recently demonstrated flexible approaches for the modular construction of such biochemical devices exclusively using DNA. These approaches have exciting implications both for engineering living cells and for mimicking life-like behavior at the nanoscale.

Attachment of Vibrio cholerae under various environmental conditions and to selected substrates

Attachment rates of Vibrio cholerae (three tox+ strains of serotype 01 and two non-01's) were examined using epifluorescent microscopy and TEM. The effects of temperature, pH, various ions and nutrient starvation on attachment were determined. Optimum attachment occurred at 35°C, pH 2, concentrations of 1.0–1.5% NaCl, 1.0–1.5% KCl, 0.5–0.1% MgCl2 (with 1.0% NaCl), and 1.0–0.5% CaCl2 (with 1.0% NaCl). After one day of starvation, attachment declined by 75% with little change during further starvation. Adhesion to a variety of non-living substrates, more than 25 species of algae, and three species of aquatic plants was examined using direct fluorescent staining, fluorescent monoclonal antibody and epifluorescent microscopy. Attachment was expressed numerically as an adhesion index. The highest rate of attachment to natural substrates occurred with (some forms of) chitin and diatomaceous earth. Highest rates on algae were noted on three species of green algae, one species of red and one species of yellow green. Since V. cholerae can readily attach to many substrates common in tropic and semi-tropical estuarine waters and under conditions typical of estuarine and marine waters, this is consistent with the hypothesis that the estuarine environment is an ideal reservoir for cholera-causing strains of V. cholerae.

Attachment of Vibrio cholerae under various environmental conditions and to selected substrates

Attachment rates of Vibrio cholerae (three tox + strains of serotype 01 and two non-01's) were examined using epifluorescent microscopy and TEM. The effects of temperature, pH, various ions and nutrient starvation on attachment were determined. Optimum attachment occurred at 35°C, pH 2, concentrations of 1.0–1.5% NaCl, 1.0–1.5% KCl, 0.5–0.1% MgCl 2 (with 1.0% NaCl), and 1.0–0.5% CaCl 2 (with 1.0% NaCl). After one day of starvation, attachment declined by 75% with little change during further starvation. Adhesion to a variety of non-living substrates, more than 25 species of algae, and three species of aquatic plants was examined using direct fluorescent staining, fluorescent monoclonal antibody and epifluorescent microscopy. Attachment was expressed numerically as an adhesion index. The highest rate of attachment to natural substrates occurred with (some forms of) chitin and diatomaceous earth. Highest rates on algae were noted on three species of green algae, one species of red and one species of yellow green. Since V. cholerae can readily attach to many substrates common in tropic and semi-tropical estuarine waters and under conditions typical of estuarine and marine waters, this is consistent with the hypothesis that the estuarine environment is an ideal reservoir for cholera-causing strains of V. cholerae.

Effect of briefings on rates of damage to corals by scuba divers

Observations were carried out in the Ras Mohammed National Park (Sharm el Sheikh, Sinai, Egypt) both to determine the rates of damage to corals by SCUBA divers and to assess the effectiveness of environmental education in reducing these. A single environmental awareness briefing reduced the rate of divers' contact with reef substrates from 1·4 to 0·4 contacts per diver per 7 min observation period. At the same time, the proportion of contacts that were voluntary, and so mainly directed at non-living substrate, increased to 63·8%. As a result, the rates of contact with living corals (as opposed to non-living substrates) decreased from 0·9 to 0·15 instances per diver per 7 min. This rate of contact prior to briefings is estimated to correspond to c. 500 potentionally damaging contacts per day at the most heavily used dive sites, equivalent to c. 15 incidents m −2 year −1.

Improvement of field sampling methods for adult Karoo paralysis ticks, Ixodes rubicundus (Acari: Ixodidae), through addition of host odour

The responsiveness of Ixodes rubicundus ticks on questing substrates and the success of their attachment to non-living substrates were investigated. The purpose of this study was to relate responsiveness to conditions of temperature and humidity, to compare the efficacy of flagging and dragging methods to estimate the size of populations of adult I. rubicundus in the field, and to determine the possible influence of host odour on the efficacy of these methods. Responsiveness was tested under varying conditions of temperature and humidity under field conditions, and the same ticks were used to determine the duration of attachment to a flannel cloth, either impregnated with host odour from sheep wool or without it. Flagging and dragging methods were compared under laboratory conditions with cloths either treated with host odour or not. Within the range of ambient temperatures recorded during this study (7-25 degrees C) most of the ticks (86%) were responsive. No obvious relationship between temperature, relative humidity and responsiveness of ticks was evident. Ticks remained on average 32.9 seconds (n = 64) on cloth treated with host odour compared to 9.1 seconds (n = 54) on untreated cloth. Flagging was 1.5-1.7 times as effective as dragging and treatment of the cloths with host odour increased the efficacy 2.4 (dragging) to 2.8 (flagging) times. The reactions of ticks to external stimuli should, therefore, be taken into account to maximize field sampling success.

Cell locomotion on differently charged substrates: Effects of substrate charge on locomotive speed of fibroblastic cells

To assess how cell locomotive behavior is influenced by an electrostatic interaction at the cells' contact area, locomotion speeds of mouse fibroblast, L cells, were compared on differently charged non-living substrates. These substrates were prepared by polymerizing bovine serum albumin with glutaraldehyde, and their surface charge was changed by treating them with poly- l-lysine or poly- l-histidine. The locomotion speeds increased with increasing negativity of the substrate charge. On the less negatively charged substrates, the cells ceased locomotion and did not alter their-positions. In spite of the diversity in the cell behavior, there was little difference in cell growth among the different substrates. When the substrates were treated with trinitrobenzene sulphonic acid (TNBS), which reacts with amino and other cationic groups, the immobilization no longer occurred. This indicates that the substrate charge is a main factor in modulating cell behavior.

Petroleum hydrocarbons inhibit decomposition of organic matter in seawater

MOTILE marine bacteria, like higher animals, have the capacity to detect and be attracted to organic substances1, including living microbial prey2. Mitchell et al.3 found that this chemotactic response was inhibited by low concentrations of hydrocarbons such as toluene, phenol and crude oil. The bacterial population was not killed but did lose its ability to detect non-living substrates as well as living prey, such as algae and enteric bacteria3–5. It seems that the ability of a marine bacterium to degrade a substrate is augmented by its attraction to that substance. This report describes the role of bacterial chemotaxis in organic matter decomposition in seawater and its inhibition by sublethal concentrations of petroleum hydrocarbons.

Growth of rust fungi of wheat and flax on chemically-defined media

THE rust fungi cause serious economic losses of wheat and other crops. In nature, these organisms complete their life cycles only on living tissues of their hosts and, until recently1, they have been regarded as obligate parasites due to their failure to grow in axenic culture on non-living substrates. We have now obtained highly reproducible vegetative growth and sporulation of the flax rust fungus, Melampsora lini (Ehrenb.) Lev. (race 3) and vegetative growth of two North American races (15B-4 and 56) of the wheat stem rust fungus, Puccinia graminis f. sp. tritici (Erikss. and Henn.) on chemically defined liquid media, sterilised by millipore filtration and seeded with uncontaminated uredospores. Vegetative growth and some sporulation were also obtained with an Australian isolate of wheat rust, race 126-ANZ 6, 7.

Bacterial chemoreception: an important ecological phenomenon inhibited by hydrocarbons

Motile marine bacteria have been shown to display chemoreception. They are attracted to a wide range of organic compounds. The response is highly specific for each micro-organism. Chemoreception is also involved in the biodegradation of phytoplankton and enteric bacteria by bacterial predators. This ability of bacteria to detect living and non-living substrates is totally inhibited by hydrocarbons. The ecological implications of this type of sublethal effect on the self-purifying capacity of the sea and on the behavior of marine animals is discussed.

Flagellar adhesion ofCrithidia fasciculata to Millipore filters

Millipore filters composed of mixed cellulose esters have been used to investigate the adhesion of flagella ofCrithidia fasciculata to a non-living substrate. After 4 days on the surface of a culture of the flagellate, one side of the filter was covered with a monolayer of cells. In most cases the flagella penetrated the pores of the filter and at one or more points along their length presumed sites of adhesion were marked by the presence of hemidesmosomes, characterized by a thickened inner leaflet of the flagellar membrane and the presence of large numbers of fine filaments. If the interstitial space of the filter was sufficiently large, the hemidesmosomes occurred at the apex of an evagination of the flagellar membrane. These evaginations are believed to arise by movement of the flagellum relative to the point of adhesion. The addition of distilled water causes de-adhesion of the flagellum and its withdrawal from the filter. The hypothesis that cells adhere to one another and to non-living substrates by different mechanisms is discussed in the light of the results obtained here.

SEEDLING BLIGHT, A FUSARIAL DISEASE OF ASPARAGUS

Incidence of seedling blight in Ontario can be correlated with proximity of mature plantations or with the presence of debris from a previous asparagus crop. As the disease was detected on seedlings grown in soil from "volunteer" plants growing in isolated habitats, the pathogen is considered to be indigenous. The pathogen penetrates directly into the embryonic region of the root tip, or through stomata on the hypocotyl, and colonizes the host both intercellularly and intracellularly. Its limitation to the cortex is regarded as unusual among the parasitic fusaria, which are mainly vascular. The fungus was identified as Fusarium oxysporum sensu Snyder & Hansen var. redolens (Wr.) Gordon. In comparison with F. moniliforme Sheldon, found to cause a root tip necrosis of asparagus seedlings, the cortical Fusarium produced less growth on basal medium plus cellulose but more growth on sucrose, and showed a greater ability to hydrolyze starch. Differing nutrient preferences are suggested as one explanation for the localized types of colonization exhibited by these two fusaria. The optimum soil temperature for disease incidence was established at 25°-30 °C. The effect of temperatures above 30 °C. is considered to be twofold: (1) inhibiting growth of the pathogen and (2) permitting the host to escape by inducing its more rapid emergence. Below 20 °C, the pre-emergence phase of the disease is favored by a retardation of the rate of emergence. Both low and high levels of soil moisture retard emergence and favor pre-emergence blight. Under greenhouse conditions, incidence of the disease usually increased more rapidly when leguminous rather than nonleguminous residues were present in the soil and there was some evidence that the saprophytic growth of the pathogen was more profuse on certain nonliving substrates.