Metapopulation Structure of Diatom-associated Marine Bacteria

Marine bacteria-phytoplankton interaction ultimately shapes ecosystem productivity. The biochemical mechanisms underlying their interactions become increasingly known, yet how these ubiquitous interactions drive bacterial evolution has not been illustrated. Here, we sequenced genomes of 294 bacterial isolates associated with 19 coexisting diatom cells. These bacteria constitute eight genetically monomorphic populations of the globally abundant Roseobacter group. Six of these populations are members of Sulfitobacter, arguably the most prevalent bacteria associated with marine diatoms. A key finding is that populations varying at the intra-specific level have been differentiated and each are either associated with a single diatom host or with multiple hosts not overlapping with those of other populations. These closely related populations further show functional differentiation; they differ in motility phenotype and they harbor distinct types of secretion systems with implication for mediating organismal interactions. This interesting host-dependent population structure is even evident for demes within a genetically monomorphic population but each associated with a distinct diatom cell, as shown by a greater similarity in genome content between isolates from the same host compared to those from different hosts. Importantly, the intra- and inter-population differentiation pattern remains when the analyses are restricted to isolates from intra-specific diatom hosts, ruling out distinct selective pressures and instead suggesting coexisting microalgal cells as physical barriers of bacterial gene flow. Taken together, microalgae-associated bacteria display a unique microscale metapopulation structure, which consists of numerous small populations whose evolution is driven by random genetic drift.

Oral Plasmablastic Lymphoma: A Case Report of an HIV Negative Patient with an Unusual Clinical Signature

Plasmablastic Lymphoma (PBL) is an aggressive variant of diffuse large B-cell lymphoma with a low survival rate. It is associated with Human Immunodeficiency Virus (HIV) infection but also affects patients with autoimmune diseases as chronic lymphocytic leukaemia, systemic lupus erythematosus and with long-term immunosuppression for heart and kidney transplants, ulcerative colitis. It has been reported in immunocompetent and HIV negative patients, determining the diagnosis more challenging. A rare case of bleeding gingival hyperplastic PBL in the left posterior mandibular area in a 61-year-old HIV negative male patient is reported. Histological assessment showed that oral mucosa was infiltrated by a monomorphic population of large lymphoid elements with morphological characteristics similar to immunoblasts with a “starry sky” appearance. Immunohistochemical markers were positive for CD138, Kappa and Lambda light chains, and negative for CKAE1/3, Synaptophysine, Chromogranin, CD56, and CD20. The detection of the primary oral manifestation of PBL remains challenging in immunocompetent patients and this case report aims to broaden the knowledge of the possible oral clinical aspects of PBL.

Optimizing mating encounters by sexually dimorphic movements

All organisms with sexual reproduction undergo a process of mating, which essentially involves the encounter of two individuals belonging to different sexes. During mate search, both sexes should mutually optimize their encounters, thus raising a question of how they achieve this. Here, we show that a population with sexually dimorphic movement patterns achieves the highest individual mating success under a limited lifespan. Extensive simulations found and analytical approximations corroborated the existence of conditions under which sexual dimorphism in the movement patterns (i.e. how diffusively they move) is advantageous over sexual monomorphism. Mutual searchers with limited lifespans need to balance the speed and accuracy of finding their mates, and dimorphic movements can solve this trade-off. We further demonstrate that the sexual dimorphism can evolve from an initial sexually monomorphic population. Our results emphasize the importance of considering mutual optimization in problems of random search.

Structural symmetry in evolutionary games

In evolutionary game theory, an important measure of a mutant trait (strategy) is its ability to invade and take over an otherwise-monomorphic population. Typically, one quantifies the success of a mutant strategy via the probability that a randomly occurring mutant will fixate in the population. However, in a structured population, this fixation probability may depend on where the mutant arises. Moreover, the fixation probability is just one quantity by which one can measure the success of a mutant; fixation time , for instance, is another. We define a notion of homogeneity for evolutionary games that captures what it means for two single-mutant states, i.e. two configurations of a single mutant in an otherwise-monomorphic population, to be ‘evolutionarily equivalent’ in the sense that all measures of evolutionary success are the same for both configurations. Using asymmetric games, we argue that the term ‘homogeneous’ should apply to the evolutionary process as a whole rather than to just the population structure. For evolutionary matrix games in graph-structured populations, we give precise conditions under which the resulting process is homogeneous. Finally, we show that asymmetric matrix games can be reduced to symmetric games if the population structure possesses a sufficient degree of symmetry.

Cutaneous myxoma in a pintagol (Sporagra magellanica X Serinus canaria)

<p>Myxomas are benign mesenchymal tumors rarely described in birds. This report describes the clinical and pathological findings in a case of myxoma in a pintagol (<bold>Sporagra magellanica</bold>X<bold> Serinus canaria</bold>). The animal had a nodule on the dorsal region of the third digit on the left hindlimb. Grossly, it was a 0.9×0.5×0.4cm, soft, white nodule, with black and yellow areas on the cut surface. Microscopically, a well-differentiated monomorphic population of spindle cells arranged in an abundant Alcian blue-positive myxoid matrix was observed. The diagnosis of myxoma was based on the microscopic findings</p>

The cytopathologic features of mammary analog secretory carcinoma and its mimics

Mammary Analogue Secretory Carcinoma (MASC) is a newly recognized neoplasm of the salivary gland, first described in 2010. This tumor harbors a unique translocation, t(12;15)(p13;q25) that results in the fusion of ETV6 with NTRK3 which produces a transformative chimeric tyrosine kinase. To date, few cases of MASC sampled by fine needle aspiration have been reported. Cytologically, MASC can be confused with other oncocytic salivary gland tumors, including Warthin-tumor, acinic cell carcinoma (AciCC) and mucoepidermoid carcinoma. It is characterized by a monomorphic population of lesional cells with round nuclei, prominent nucleoli and abundant, eosinophilic foamy cytoplasm; forming papillary groups with transgressing vessels. Though, based on cytomorphology alone, the definite diagnosis can be challenging, in conjunction with available clinical clues (i.e. male patient, extra-parotid site) MASC should be included in the differential diagnosis of FNA specimens diagnosed as oncocytic salivary gland neoplasms or suspicious for AciCC. Here we present a case of MASC with FNA sampling at our institution.

How to make a kin selection model when marginal fitness is non-linear?

We observe that the Taylor-Frank method for making kin selection models when fitness $w$ is a nonlinear function of a continuous actor's phenotype $y$ and the average phenotype $z$ in its social environment requires $w(y,z)$ to be differentiable (as a function of two variables, i.e., jointly in $y$ and $z$). This means that even if $w(y,z)$ is non-linear globally, locally it must be close to linear, meaning that its graph must be well approximated by a plane. When more than two individuals interact, this assumption is only satisfied when the marginal fitness of the actor is a linear function of the fraction of individuals in its social environment that share its phenotype. This assumption sometimes fails for biologically important fitness functions, for instance in microbial data and the theory of repeated n-person games. In these cases, the Taylor-Frank methodology cannot be used, and a more general form of direct fitness must replace it, to decide when a social mutant allele can invade a monomorphic population.

Granulocytic Sarcoma of Parotid Gland in a 4-Year-Old Child with Subleukemic AML: A Diagnostic Challenge!

A 4-year-old male child presented to our outpatient department with large swelling in the parotid region. Routine investigations were all within normal limits, and evaluation of complete blood count was normal except for anaemia. Excisional biopsy as a therapeutic diagnosis was done. Microscopic examination showed monomorphic population of discohesive, hyperchromatic small round cells having high N : C ratio, coarse chromatin, conspicuous nucleoli, and sometimes angulated nuclei lying in sheets. Immunohistochemistry was done to rule out possible differential diagnosis. Fine needle aspiration from the swelling showed predominant population of blast cells. Myeloperoxidase and PBO were strongly positive, and diagnosis of granulocytic sarcoma was confirmed.

Malignant or benign leukocytosis

Leukocytosis, or elevated WBC count, is a commonly encountered laboratory finding. Distinguishing malignant from benign leukocytosis is a critical step in the care of a patient, which initiates a vastly different decision tree. Confirmation of the complete blood cell count and the WBC differential is the first step. Examination of the PB smear is essential to confirming the automated blood cell differential or affirming the manual differential performed on the PB smear. Next is separation of the leukocytosis into a myeloid versus a lymphoid process. Distinguishing a reactive lymphoid proliferation from a lymphoproliferative disorder requires examination of lymphocyte morphology for pleomorphic lymphocytes versus a monomorphic population, with the latter favoring a lymphoproliferative neoplasm. Samples suspicious for lymphoproliferative disorders can be confirmed and characterized by flow cytometry, with molecular studies initiated in select cases; precursor lymphoid neoplasms (lymphoblasts) should trigger a BM examination. Myeloid leukocytosis triggers a differential diagnosis of myeloid leukemoid reactions versus myeloid malignancies. The manual differential is key, along with correct enumeration of blasts and blast equivalents, immature granulocytes, basophils, and eosinophils and identifying dysplasia to identify myeloid malignancies. Confirmation and characterization of myeloid malignancies should be performed with a BM examination and the appropriate ancillary studies. Myeloid leukemoid reactions commonly result from infections and show activated neutrophil changes on morphology; these should prompt evaluation for infection. Other causes of reactive myeloid leukocytoses are also discussed herein.

Presumptive pure erythroid leukemia in a dog

A 6.5-year-old, intact male Cocker Spaniel dog was referred with a history of depression and anorexia of 1-week duration. Mucosal pallor was prominent on physical examination. Complete blood cell count revealed pancytopenia and occasional blast cells. Bone marrow aspirate cytology indicated that individual particles were composed of approximately 60% hematopoietic cells and a monomorphic population of blast cells with perfectly round nuclei, consistent paranuclear clearing, and deeply basophilic cytoplasm devoid of granules dominating the marrow fields. The granulocytic lineage was severely decreased with a granulocytic-to-erythroid ratio of 0.15 and a blast cell percentage of at least 70% of all nucleated cells; the myeloblasts and monoblasts composed <5% of nonerythroid cells. Bone marrow cytology slides were submitted for immunocytochemical immunophenotyping using antibodies to myeloperoxidase, cluster of differentiation (CD)3, CD79a, CD11b, CD45, and CD34. The neoplastic cells did not express any of the antigens assessed. The combination of light microscopic cytomorphology and the immunophenotype were strongly suggestive of pure erythroid leukemia.