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PubMed2002

Speciation and phylogeography in the cosmopolitan marine moon jelly, Aurelia sp.

BACKGROUND: The cosmopolitan moon jelly Aurelia is characterized by high degrees of morphological and ecological plasticity, and subsequently by an unclear taxonomic status. The latter has been revised repeatedly over the last century, dividing the genus Aurelia in as many as 12 or as little as two species. We used molecular data and phenotypic traits to unravel speciation processes and phylogeographic patterns in Aurelia. RESULTS: Mitochondrial and nuclear DNA data (16S and ITS-1/5.8S rDNA) from 66 world-wide sampled specimens reveal star-like tree topologies, unambiguously differentiating 7 (mtDNA) and 8 (ncDNA) genetic entities with sequence divergences ranging from 7.8 to 14% (mtDNA) and 5 to 32% (ncDNA), respectively. Phylogenetic patterns strongly suggest historic speciation events and the reconstruction of at least 7 different species within Aurelia. Both genetic divergences and life history traits showed associations to environmental factors, suggesting ecological differentiation forced by divergent selection. Hybridization and introgression between Aurelia lineages likely occurred due to secondary contacts, which, however, did not disrupt the unambiguousness of genetic separation. CONCLUSIONS: Our findings recommend Aurelia as a model system for using the combined power of organismic, ecological, and molecular data to unravel speciation processes in cosmopolitan marine organisms.

Animals↗
PubMed2005

Out of Tanganyika: genesis, explosive speciation, key-innovations and phylogeography of the haplochromine cichlid fishes.

BACKGROUND: The adaptive radiations of cichlid fishes in East Africa are well known for their spectacular diversity and their astonishingly fast rates of speciation. About 80% of all 2,500 cichlid species in East Africa, and virtually all cichlid species from Lakes Victoria (approximately 500 species) and Malawi (approximately 1,000 species) are haplochromines. Here, we present the most extensive phylogenetic and phylogeographic analysis so far that includes about 100 species and is based on about 2,000 bp of the mitochondrial DNA. RESULTS: Our analyses revealed that all haplochromine lineages are ultimately derived from Lake Tanganyika endemics. We find that the three most ancestral lineages of the haplochromines sensu lato are relatively species poor, albeit widely distributed in Africa, whereas a fourth newly defined lineage - the 'modern haplochromines' - contains an unparalleled diversity that makes up more than 7% of the worlds' approximately 25,000 teleost species. The modern haplochromines' ancestor, most likely a riverine generalist, repeatedly gave rise to similar ecomorphs now found in several of the species flocks. Also, the Tanganyikan Tropheini are derived from that riverine ancestor suggesting that they successfully re-colonized Lake Tanganyika and speciated in parallel to an already established cichlid adaptive radiation. In contrast to most other known examples of adaptive radiations, these generalist ancestors were derived from highly diverse and specialized endemics from Lake Tanganyika. A reconstruction of life-history traits revealed that in an ancestral lineage leading to the modern haplochromines the characteristic egg-spots on anal fins of male individuals evolved. CONCLUSION: We conclude that Lake Tanganyika is the geographic and genetic cradle of all haplochromine lineages. In the ancestors of the replicate adaptive radiations of the 'modern haplochromines', behavioral (maternal mouthbrooding), morphological (egg-spots) and sexually selected (color polymorphism) key-innovations arose. These might be - together with the ecological opportunity that the habitat diversity of the large lakes provides - responsible for their evolutionary success and their propensity for explosive speciation.

Animals↗
PubMed1977

Questions concerning environmental mobility of arsenic: needs for a chemical data base and means for speciation of trace organoarsenicals.

Biomethylation of metals, including arsenic, apparently occurs as a global process. Health control strategies therefore depend on accurate analysis of arsenic's environmental mobility. Determining to what extent biotransformations occur and how resultant organometal(loids) are sequestered in food chains requires sophistication beyond present-day total element determinations. Rather, active molecular forms of arsenic must be speciated for each environmental compartment, and it is necessary to quantify the dynamics of arsenic's mobility. Thus, new chemical facts are needed yielding rates of methylation or demethylation of arsenic; partition coefficients of organoarsenicals between air, water, and organic phases; and arsenic redox chemistry in polar media. NBS research in this context is reviewed with examples of recent results emphasizing speciation methodology. Topic areas discussed are: the nature of aquated methylarsenic species (NMR and laser-Raman spectroscopy); transport of methylarsenicals from aqueous media (gas chromatography-graphic furnace AA detection applied to metabolic Me3As formation); and speciation of involatile organoarsenicals in aqueous media (demonstration of HPLC utilizing element-specific AA detection and appraisal of electrochemical detectors).

Air↗
PubMed1995

Trace metals speciation by HPLC with plasma source mass spectrometry detection.

The analysis of environmental and biological samples often requires detection at the parts per billion (ppb) level. Plasma source mass spectrometry has potential as a method for the analysis and speciation of trace elements. This is due to the technique's highly selective nature and excellent sensitivity. In comparison to atomic emission detection, detection limits are usually two to three orders of magnitude lower for plasma MS determinations. Interfacing HPLC with plasma MS provides a means of separation that is necessary for speciation. Speciation involves the determination and quantitation of the various chemical forms of a particular element. A host of HPLC-ICP-MS techniques may be used to obtain this information. This brief report will focus on the most recent work in this area, with emphasis on the work done in our laboratory.

Chromatography, Gel↗
PubMed2005

Speciation of chromium via laser-induced breakdown spectroscopy of ion exchange polymer membranes.

A new method for the speciation of ng/mL concentrations of Cr(III) and Cr(VI) solutions with analysis by laser-induced breakdown spectroscopy (LIBS) is reported. Speciation is achieved by pre-concentration of the chromium onto commercially available cation exchange polymer membranes. Chromium(III) is removed directly by cation exchange; chromium(VI) in the filtrate is reduced to Cr(III) and concentrated onto a second cation exchange membrane, affording independent measurement of both species. Large volumes of waters containing Cr(III) and Cr(VI) can be concentrated onto the membranes and directly analyzed by laser-induced breakdown spectroscopy. The estimated limit of detection corresponds to 500 ng of Cr on the membrane: if a solution volume of 1 L is used, then the detection limit corresponds to a solution concentration of 0.5 ng/mL. Excellent separation of the chromium species is attained. Results show that overall method efficiencies range from 94-116% and are independent of the matrix. The influence of pH has been measured, and although Cr(VI) converts to Cr(III) in acidic solutions, the total Cr recoveries are not appreciably influenced by pH over the range of natural waters (4 to 9). In addition, speciation was performed in the presence of a number of different cations and showed that the method is robust in many different and complex matrices.

Chromium↗
PubMed2006

Laser-induced breakdown spectroscopy for ambient air particulate monitoring: correlation of total and speciated aerosol particle counts.

A statistical analysis of ambient air particle monitoring, namely PM2.5, is presented to elucidate the correlations between laser-induced breakdown spectroscopy (LIBS)-based speciated aerosol monitoring and non-speciated aerosol monitoring (i.e., total particle counts). LIBS was used in a real-time, conditional-processing mode to identify individual aerosol particles containing detectable quantities of either calcium or sodium, as based on the resulting atomic emission signals. Using this technique, real-time measurements of speciated aerosol particle concentrations and analyte mass concentrations were evaluated for a total of 60 1-hour sampling periods spread over a 5-week period. For each 1-hour sampling period, total aerosol counts were simultaneously monitored using a commercial light scattering-based instrument. Over the 30 sampling periods, aerosol counts (both total and LIBS-based) were found to vary by more than one order of magnitude. For aerosol particles in the 500 nm to 2.5 microm size range, significant correlations were found between the two sampling methods, resulting in correlation coefficients (r2) ranging from 0.22 to 0.93. In addition, transient fluctuations in aerosol counts on a timescale of 5 to 10 minutes were successfully observed simultaneously with the two monitoring techniques, thereby demonstrating the temporal resolution of LIBS.

Aerosols↗
PubMed2004

The genetics of speciation by reinforcement.

Reinforcement occurs when natural selection strengthens behavioral discrimination to prevent costly interspecies matings, such as when matings produce sterile hybrids. This evolutionary process can complete speciation, thereby providing a direct link between Darwin's theory of natural selection and the origin of new species. Here, by examining a case of speciation by reinforcement in Drosophila,we present the first high-resolution genetic study of variation within species for female mating discrimination that is enhanced by natural selection. We show that reinforced mating discrimination is inherited as a dominant trait, exhibits variability within species, and may be influenced by a known set of candidate genes involved in olfaction. Our results show that the genetics of reinforced mating discrimination is different from the genetics of mating discrimination between species, suggesting that overall mating discrimination might be a composite phenomenon, which in Drosophila could involve both auditory and olfactory cues. Examining the genetics of reinforcement provides a unique opportunity for both understanding the origin of new species in the face of gene flow and identifying the genetic basis of adaptive female species preferences, two major gaps in our understanding of speciation.

Animals↗
PubMed2005

Genomic islands of speciation in Anopheles gambiae.

The African malaria mosquito, Anopheles gambiae sensu stricto (A. gambiae), provides a unique opportunity to study the evolution of reproductive isolation because it is divided into two sympatric, partially isolated subtaxa known as M form and S form. With the annotated genome of this species now available, high-throughput techniques can be applied to locate and characterize the genomic regions contributing to reproductive isolation. In order to quantify patterns of differentiation within A. gambiae, we hybridized population samples of genomic DNA from each form to Affymetrix GeneChip microarrays. We found that three regions, together encompassing less than 2.8 Mb, are the only locations where the M and S forms are significantly differentiated. Two of these regions are adjacent to centromeres, on Chromosomes 2L and X, and contain 50 and 12 predicted genes, respectively. Sequenced loci in these regions contain fixed differences between forms and no shared polymorphisms, while no fixed differences were found at nearby control loci. The third region, on Chromosome 2R, contains only five predicted genes; fixed differences in this region were also verified by direct sequencing. These "speciation islands" remain differentiated despite considerable gene flow, and are therefore expected to contain the genes responsible for reproductive isolation. Much effort has recently been applied to locating the genes and genetic changes responsible for reproductive isolation between species. Though much can be inferred about speciation by studying taxa that have diverged for millions of years, studying differentiation between taxa that are in the early stages of isolation will lead to a clearer view of the number and size of regions involved in the genetics of speciation. Despite appreciable levels of gene flow between the M and S forms of A. gambiae, we were able to isolate three small regions of differentiation where genes responsible for ecological and behavioral isolation are likely to be located. We expect reproductive isolation to be due to changes at a small number of loci, as these regions together contain only 67 predicted genes. Concentrating future mapping experiments on these regions should reveal the genes responsible for reproductive isolation between forms.

Animals↗
PubMed2001

Population structure and speciation in tropical seas: global phylogeography of the sea urchin Diadema.

The causes of speciation in the sea are rarely obvious, because geographical barriers are not conspicuous and dispersal abilities or marine organisms, particularly those of species with planktonic larvae, are hard to determine. The phylogenetic relations of species in cosmopolitan genera can provide information on the likely mode of their formation. We reconstructed the phylogeny of the pantropical and subtropical sea urchin genus Diadema, using sequences of mitochondrial DNA from 482 individuals collected around the world, to determine the efficacy of barriers to gene flow and to ascertain the history of possible dispersal and vicariance events that led to speciation. We also compared 22 isozyme loci between all described species except D. palmeri. The mitochondrial DNA data show that the two deepest lineages are found in the Indian and West Pacific Oceans. (Indo-Pacific) Diadema setosum diverged first from all other extant Diadema, probably during the initiation of wide fluctuations in global sea levels in the Miocene. The D. setosum clade then split 3-5 million years ago into two clades, one found around the Arabian Peninsula and the other in the Indo-West Pacific. On the lineage leading to the other species of Diadema, the deepest branch is composed of D. palmeri, apparently separated when the climate of New Zealand became colder and other tropical echinoids at these islands went extinct. The next lineage to separate is composed of a currently unrecognized species of Diadema that is found at Japan and the Marshall Islands. Diadema mexicanum in the eastern Pacific separated next, whereas D. paucispinum, D. savignyi, and D. antillarum from the western and central Atlantic, and (as a separate clade) D. antillarum from the eastern Atlantic form a shallow polytomy. Apparently, Indo-Pacific populations of Diadema maintained genetic contact with Atlantic ones around the southern tip of Africa for some time after the Isthmus of Panama was complete. Diadema paucispinum contains two lineages: D. paucispinum sensu stricto is not limited to Hawaii as previously thought, but extends to Easter Island, Pitcairn, and Okinawa; A second mitochondrial clade of D. paucispinum extends from East Africa and Arabia to the Philippines and New Guinea. A more recent separation between West Indian Ocean and West Pacific populations was detected in D. setosum. Presumably, these genetic discontinuities are the result of water flow restrictions in the straits between northern Australia and Southeast Asia during Pleistocene episodes of low sea level. Diadema savignyi is characterized by high rates of gene flow from Kiribati in the central Pacific all the way to the East African Coast. In the Atlantic, there is a biogeographic barrier between the Caribbean and Brazil, possibly caused by fresh water outflow from the Amazon and the Orinoco Rivers. Diadema antillarum populations of the central Atlantic islands of Ascension and St. Helena are genetically isolated and phylogenetically derived from Brazil. Except for its genetic separation by the mid-Atlantic barrier, Diadema seems to have maintained connections through potential barriers to dispersal (including the Isthmus of Panama) more recently than did Eucidaris or Echinometra, two other genera of sea urchins in which phylogeography has been studied. Nevertheless, the mtDNA phylogeography of Diadema includes all stages expected from models of allopatric differentiation. There are anciently separated clades that now overlap in their geographic distribution, clades isolated in the periphery of the genus range that have remained in the periphery, clades that may have been isolated in the periphery but have since spread towards the center, closely related clades on either side of an existing barrier, and closely related monophyletic entities on either side of an historical barrier that have crossed the former barrier line, but have not attained genetic equilibrium. Except for D. paucispinum and D. savignyi, in which known hybridization may have lodged mtDNA from one species into the genome of the other, closely related clades are always allopatric, and only distantly related ones overlap geographically. Thus, the phylogenetic history and distribution of extant species of Diadema is by and large consistent with allopatric speciation.

Adenosine Triphosphatases↗
PubMed2005

Habitat avoidance: overlooking an important aspect of host-specific mating and sympatric speciation?

Understanding speciation requires discerning how reproductive barriers to gene flow evolve between previously interbreeding populations. Models of sympatric speciation for phytophagous insects posit that reproductive isolation can evolve in the absence of geographic isolation as a consequence of an insect shifting and ecologically adapting to a new host plant. One important adaptation contributing to sympatric differentiation is host-specific mating. When organisms mate in preferred habitats, a system of positive assortative mating is established that facilitates sympatric divergence. Models of host fidelity generally assume that host choice is determined by the aggregate effect of alleles imparting positive preferences for different plant species. But negative effect genes for avoiding nonnatal plants may also influence host use. Previous studies have shown that apple and hawthorn-infesting races of Rhagoletis pomonella flies use volatile compounds emitted from the surface of fruit as key chemosensory cues to recognize and distinguish between their host plants. Here, we report results from field trials indicating that in addition to preferring the odor of their natal fruit, apple and hawthorn flies, and their undescribed sister species infesting flowering dogwood (Cornus florida), also avoid the odors of nonnatal fruit. We discuss the implications of nonnatal fruit avoidance for the evolutionary dynamics and genetics of sympatric speciation. Our findings reveal an underappreciated role for habitat avoidance as a potential postmating, as well as prezygotic, barrier to gene flow.

Animals↗
PubMed2004

Uranium complexation and uptake by a green alga in relation to chemical speciation: the importance of the free uranyl ion.

The bioavailability and toxicity of dissolved metals are closely linked to the metals' chemical speciation in solution. Normally the complexation of a metal by a ligand would be expected to decrease its bioavailability. The aqueous speciation of uranium (U) undergoes tremendous changes in the presence of ligands commonly found in natural waters (carbonate, phosphate, hydroxide, and natural organic matter). In the present project, links between speciation, medium composition, and bioavailability of uranium toward Chlamydomonas reinhardtii, a unicellular green alga, were investigated. Short-term metal uptake rates were determined in simple inorganic media at constant low pH (5.0) and hardness with particular emphasis on the differentiation between adsorbed and intracellular metal. While intracellular uptake was fairly linear over 1 h, partly reversible adsorption reached steady-state within minutes. Both adsorption and absorption were saturable processes (with a half-saturation constant Km of 0.51 microM). Addition of phosphate, citrate, or ethylenediaminetetraacetic acid (EDTA) as ligands decreased uranium bioavailability. No evidence indicating the transport of intact uranyl complexes was found (i.e., facilitated diffusion of metal bound to an assimilable ligand such as uranium-phosphate complexes). Within these experimental conditions, uranium uptake was correlated with the free uranyl ion concentration as predicted by the free-ion activity model (FIAM) and biotic ligand model (BLM).

Absorption↗
PubMed2005

Soil-solution speciation of Cd as affected by soil characteristics in unpolluted and polluted soils.

Total metal content by itself is insufficient as a measure to indicate actual environmental risk. Understanding the mobility of heavy metals in the soil and their speciation in the soil solution is of great importance for accurately assessing environmental risks posed by these metals. In a first explorative study, the effects of general soil characteristics on Cd mobility were evaluated and expressed in the form of empirical formulations. The most important factors influencing mobility of Cd proved to be pH and total soil content. This may indicate that current legislation expressing the requirement for soil sanitation in Flanders (Belgium) as a function of total soil content, organic matter, and clay does not successfully reflect actual risks. Current legal frameworks focusing on total content, therefore, should be amended with criteria that are indicative of metal mobility and availability and are based on physicochemical soil properties. In addition, soil-solution speciation was performed using two independent software packages (Visual Minteq 2.23 and Windermere Humic Aqueous model VI [WHAM VI]). Both programs largely were in agreement in concern to Cd speciation in all 29 soils under study. Depending on soil type, free ion and the organically complexed forms were the most abundant species. Additional inorganic soluble species were sulfates and chlorides. Minor species in solution were in the form of nitrates, hydroxides, and carbonates, the relative importance of which was deemed insignificant in comparison to the four major species.

Belgium↗
PubMed2006

Effect of pH on metal speciation and resulting metal uptake and toxicity for earthworms.

In the present study, relationships between changes in the solubility and speciation of metals in contaminated soils under different pH regimes and their toxicity to earthworms were investigated. Earthworms (Lumbricus rubellus) were exposed in a laboratory bioassay to metalliferous soils under three pH regimes: Unamended pH, pH lowered by one unit (pH -1), and pH increased by one unit (pH +1). In each soil, total (hot nitric acid-extractable) and 0.01 M CaCl2-extractable metal concentrations were measured and soil pore-water chemistry analyzed to allow metal speciation to be modeled using the Windermere Humic Aqueous Model. Earthworm metal accumulation was determined and toxicity assessed by measuring survival and reproduction and at the molecular level by recording expression of the gene encoding metallothionein-2 (MT-2) using quantitative reverse transcriptase-polymerase chain reaction. Both metal solubility and speciation were found to be highly pH dependent. Metal accumulation in earthworms was influenced by soil concentration and, in some cases (e.g., Cd), by pH. Reproduction was affected (reduced up to 90%) by soil metal level, pH, and their interaction. Relationships between analyzed and calculated Zn concentrations and toxicity and between analyzed and calculated Cd concentrations and tissue accumulation and MT-2 expression were compared by fitting dose-response models and assessing the fit of the data. This analysis indicated that values based on a pH-adjusted free ion concentration best explained toxicity (r2 = 0.82) and accumulation (r2 = 0.54). Expression of MT-2 was, however, poorly correlated (p > 0.05) with all analyzed and modeled soil metal concentrations.

Animals↗
PubMed2006

Chemical speciation of trace metals in seawater: a review.

The recent development of the chemical speciation of trace metals in seawater is described. The speciation studies reveal that metal ion complexation is one of the most important processes in seawater; especially, most bioactive trace metals, such as Fe(III) and Cu, exist as complexes with ligands in dissolved organic matter. The organic ligands in seawater are characterized with metal ions selected by the HSAB concept. A strong organic ligand, which originates from marine microorganisms, is classified as a hard base including carboxylates. The free organic ligand concentrations in seawater are buffered by complexation with excess amounts of Ca and Mg in seawater. The chemical equilibrium model suggested that the concentrations of bioactive free metal ions are at an optimal level to activities of marine microorganisms. For chemical speciation, it is important to have a better understanding of the ecological roles of trace metals in seawater.

Journal Article↗
PubMed2006

The role of in situ unit operation/process infiltration treatment on partitioning and speciation of rainfall-runoff.

Management decisions regarding the potential fate and toxicity of anthropogenic metal elements requires a knowledge of metal partitioning and speciation as mediated by in situ control systems (ICS). This study focussed on Cd, Zn, Cu and Pb, common anthropogenic metal elements generated in the built environment and examined the influence of variable event-based hydrology and passive ICS by an engineered partial exfiltration reactor (PER) system on partitioning and speciation. The feasibility and efficiency of the PER as an in situ stormwater runoff control strategy to attenuate levels of metal elements was evaluated. Results indicate that higher rainfall intensity resulted in higher dissolved fraction (fd) values for influent Zn, Cu and Cd, but did not have a significant influence on partitioning of Pb. Speciation indicated that divalent fractions of Cd, Zn, Cu and Pb were changed marginally by the PER. Cu and Pb mainly complexed with organic matter in the influent, while carbonate complexes of these metals in the effluent significantly increased. The PER consistently and statistically reduced all loadings of Cd, Cu, Pb and Zn for all examined events, whether on a mass or concentration basis. As an unsaturated flow unit operation/process the PER can efficiently remove ionic or complexed forms of metal elements. Such UOPs are a potential quality and quantity ICS strategy for rainfall-runoff.

Cities↗
PubMed1994

Speciation of vanadium(IV) and vanadium(V) using ion-exchange chromatography and ICP-AES.

A speciation method for vanadium(IV) and vanadium(V) is presented that uses a combination of HPLC and ICP-AES. In this method, 1 mM HNO3 solution and 100 mM HNO3 solution were applied in sequence as eluent. A vanadium(IV) and vanadium(V) mixture was injected into a HPLC anion-exchange column; and vanadium(IV) cation was then eluted by 1 mM HNO3, while vanadium(V) oxoacid anion was trapped on the column. After this separation, vanadium(V) was eluted as a cation from the column by 100 mM HNO3. Vanadium was detected by ICP-AES. In this separation, about 15% of vanadium(V) interfered with vanadium(IV), and trace vanadium(IV) interfered with vanadium(V). This interference could be estimated by simple calculation based on standard observations, and the speciation of vanadium(IV) and vanadium(V) was performed. The lower determination limit was 1 microgram/mL, which is insufficient to speciate vanadium sampled by conventional sampling methods in a working environment. However, impurity of the other valent vanadium species in a vanadium(V) reagent can be determined by the present method, which should be valuable in precisely assessing the toxicities of vanadium species.

Chromatography, High Pressure Liquid↗
PubMed1996

Current techniques in mycobacterial detection and speciation.

Tuberculosis, a health concern so well controlled in recent decades that eradication seemed imminent, is once again reaching epidemic proportions following the increasing prevalence of AIDS. One important means of curbing this resurgence is a robust method that has the capability of identifying and speciating mycobacterial infections in a matter of days. Classic biochemical techniques, which require 4 to 8 weeks to identify and speciate tuberculosis infections, are in the process of being replaced by newer methods, including BACTEC, gene probes, nucleic acid amplification, amplification of ribosomal RNA, high-performance liquid chromatography, and gas chromatography-mass spectrometry. This review is intended to give the reader a synopsis of the current literature and research on these methods, including reliability, approximate time required for detection and speciation, and clinical utility.

Bacteriological Techniques↗
PubMed2000

PCR-RFLP-mediated detection and speciation of bacterial species causing endophthalmitis.

PURPOSE: To determine the usefulness of polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) in the identification and speciation of bacteria causing endophthalmitis. METHODS: PCR-RFLP was performed on 53 strains of 14 bacterial species (eight Gram positive and five Gram negative) collected from both keratitis and endophthalmitis patients. Two pairs of oligonucleotide primers based on the 16S rDNA gene were used to PCR-amplify 1.2- and 1.0-kb fragments of bacterial genomic DNA. RFLPs within the PCR product were used to speciate the organisms. RESULTS: The sensitivity of the nested PCR amplification reaction was one organism. All bacteria tested could be identified and speciated using RFLP analysis except for Escherichia coli and Serratia marcescens, which could not be interdifferentiated using RFLP. Molecular analysis of two vitreous samples from two eyes with typical signs of bacterial endophthalmitis confirmed the presence of E. coli in the vitreous from a culture-positive case with E. coli endophthalmitis and revealed the presence of Staphylococcus epidermidis in the vitreous of a culture-negative case. CONCLUSIONS: It is expected that this technique will provide a useful laboratory tool for future microbiologic diagnosis of patients presenting with endophthalmitis, especially for those eyes that prove culture negative.

Bacterial Typing Techniques↗