Metagenomic Insights Into the Microbial Iron Cycle of Subseafloor Habitats.

Microbial iron cycling influences the flux of major nutrients in the environment (e.g., through the adsorptive capacity of iron oxides) and includes biotically induced iron oxidation and reduction processes. The ecological extent of microbial iron cycling is not well understood, even with increased sequencing efforts, in part due to limitations in gene annotation pipelines and limitations in experimental studies linking phenotype to genotype. This is particularly true for the marine subseafloor, which remains undersampled, but represents the largest contiguous habitat on Earth. To address this limitation, we used FeGenie, a database and bioinformatics tool that identifies microbial iron cycling genes and enables the development of testable hypotheses on the biogeochemical cycling of iron. Herein, we survey the microbial iron cycle in diverse subseafloor habitats, including sediment-buried crustal aquifers, as well as surficial and deep sediments. We inferred the genetic potential for iron redox cycling in 32 of the 46 metagenomes included in our analysis, demonstrating the prevalence of these activities across underexplored subseafloor ecosystems. We show that while some processes (e.g., iron uptake and storage, siderophore transport potential, and iron gene regulation) are near-universal, others (e.g., iron reduction/oxidation, siderophore synthesis, and magnetosome formation) are dependent on local redox and nutrient status. Additionally, we detected niche-specific differences in strategies used for dissimilatory iron reduction, suggesting that geochemical constraints likely play an important role in dictating the dominant mechanisms for iron cycling. Overall, our survey advances the known distribution, magnitude, and potential ecological impact of microbe-mediated iron cycling and utilization in sub-benthic ecosystems.

Canine Gastric Carcinomas: A Histopathological and Immunohistochemical Study and Similarities with the Human Counterpart.

Canine gastric carcinoma (CGC) affects both sexes in relatively equal proportions, with a mean age of nine years, and the highest frequency in Staffordshire bull terriers. The most common histological subtype in 149 CGC cases was the undifferentiated carcinoma. CGCs were associated with increased chronic inflammation parameters and a greater chronic inflammatory score when Helicobacter spp. were present. Understanding the molecular pathways of gastric carcinoma is challenging. All markers showed variable expression for each subtype. Expression of the cell cycle regulator 14-3-3σ was positive in undifferentiated, tubular and papillary carcinomas. This demonstrates that 14-3-3σ could serve as an immunohistochemical marker in routine diagnosis and that mucinous, papillary and signet-ring cell (SRC) carcinomas follow a 14-3-3σ independent pathway. p16, another cell cycle regulator, showed increased expression in mucinous and SRC carcinomas. Expression of the adhesion molecules E-cadherin and CD44 appear context-dependent, with switching within tumor emboli potentially playing an important role in tumor cell survival, during invasion and metastasis. Within neoplastic emboli, acinar structures lacked expression of all markers, suggesting an independent molecular pathway that requires further investigation. These findings demonstrate similarities and differences between dogs and humans, albeit further clinicopathological data and molecular analysis are required.

Cutaneous Spindle Cell Squamous Cell Carcinoma in Cats: Clinical, Histological, and Immunohistochemical Study.

This study describes the clinical and pathological characteristics of cutaneous spindle cell squamous cell carcinoma (SCSCC) in 18 cats. The average age of the cats was 11.8 ± 2.7 years, and all tumors were located in the facial skin, mainly affecting the pinna (13/18, 72%), followed by the periorbital area (4/18, 22%) and the dorsal muzzle (1/18, 6%). Tumors were composed of fusiform neoplastic cells with moderate atypia arranged in solid sheets or fascicles with foci of squamous differentiation. A panel of antibodies against cytokeratins, vimentin, S-100 protein, NSE, GFAP, Melan A, SMA, desmin, CD18, CD31, and p63 was used to help differentiate SCSCC from other spindle cell malignancies. SCSCCs expressed CK5/6 (17/18, 94%), AE1/AE3 (15/18, 83%), and p63 protein (18/18, 100%), but there was no immunolabeling for CK8/18. A role for sunlight exposure in the pathogenesis of the tumors was suggested by changes indicative of actinic keratosis, the location of the tumors in dorsal areas, and the absence of histomorphologic features of papillomavirus infection. Recurrence was not recorded in 14/18 cases (78%) during a follow-up period of 7 to 25 months. Three of 18 (17%) tumors recurred or led to humane euthanasia due to local progression, and one case (5%) had regional lymph node metastasis. Clinical outcome varied with cutaneous location, mitotic count, and invasion of surgical margins; thus, SCSCCs with a more aggressive behavior were located in the periorbital area (4/4 cases), had ≥14 mitoses in 10 high-power fields (2.37 mm2) (4/4 cases), and showed invasion of surgical margins (3/4 cases).

Canine Tonsillar Polyps: Characteristics, Classification, and Review of the Pathogenesis.

Canine tonsillar polyps are uncommon. We describe 14 tonsillar polyps in dogs and review their classification and pathogenesis. All dogs were adult (3-13 years old). Females (10/14) were more affected than males (4/14). Most of the lesions were asymptomatic (10/14). All lesions were unilateral, pedunculated (9/14), or sessile (5/14), with a smooth (12/14) or papillary/verrucous surface (2/14). Histologically, polyps consisted of benign proliferation of lymphatic vessels, blood vessels, fibrous tissue, and lymphoid tissue in variable proportions, with occasional adipose tissue (4/14). According to the main stromal components, polyps were categorized as lymphangiomatous (5/14), lymphangiolipomatous (2/14), lymphangiofibromatous (2/14), angiofibromatous (1/14), angiofibrolipomatous (1/14), lymphoid (2/14), and myxomatous (1/14). As the pathogenesis of these polyps remains unclear, we propose to replace the term inflammatory tonsillar polyp by a morphological diagnosis based on the stromal characteristics of the lesions. Simple surgical excision was curative in the 9 cases with available follow-up information.

Study on the Role of Histochemical Stains in Identifying Merkel Cells in Dogs.

Merkel cells (MCs) are neuroendocrine cells involved with tactile sense, growth, differentiation, and homeostasis of the skin as well as in different cutaneous diseases. Specific staining techniques are required for their identification because they are not easily visible in paraffin sections stained with hematoxylin and eosin. The present study assess the histochemical features of the MCs in dogs comparing with those described for other mammals in the literature and with the use of immunohistochemistry. A systematic study of samples from MCs-rich areas from healthy dogs was carried out by use of several histologic stains, including metachromatic staining, silver stains, methylene blue, periodic acid-Schiff stain, and osmium-based staining method. MCs were detected by the Grimelius argyrophilic stain in 86.7% of the specimens. The staining was showed as dark-brown granular cytoplasmic and consistently polarized to the basal cell cytoplasm matching with the cellular distribution of the characteristic neurosecretory granules. Some modifications in the standard staining protocol, including rinsing, silver reimpregnation, and counterstain dye, enhanced the MCs identification in stratified squamous epithelium. When compared with Cytokeratin 20-immunolabeled serial sections several MCs appeared nonstained with the argyrophilic method. These differences in MC numbers between stains were statistically significant. Other histologic stains failed to identify MCs in the specimens. The results of this study indicate that Grimelius argyrophilic stain is a suitable method for demonstration of MCs in the stratified squamous epithelium of skin and mucosa. Discussion on its utility when compared with immunohistochemistry and a review of the scientific literature is also presented. Anat Rec, 302:1458-1464, 2019. © 2018 Wiley Periodicals, Inc.

Mandibular odontogenic sarcoma (ameloblastic fibrodentinosarcoma) in an aged cat - Short communication.

A 13-year-old male cat presented with an ill-defined mass in the rostral mandible causing destruction and loss of alveolar bone. Microscopically, the mass consisted of cords or islands of benign odontogenic epithelium and a malignant, pleomorphic spindle-shaped cell component with dysplastic dentine formation. Immunohistochemically, neoplastic mesenchymal cells proved to be strongly positive for vimentin and negative for cytokeratins, desmin, actin and S100 protein; the Ki67 proliferation index was high. Morphological and immunohistochemical features largely overlap those reported for ameloblastic fibrodentinosarcoma, an uncommon histologic subtype of odontogenic sarcoma recognised in humans but no reported previously in animals. Ki-67 expression assessment may help to discriminate between malignant and benign forms of odontogenic tumours but the final diagnosis is mainly morphological.

In-situ incubation of iron-sulfur mineral reveals a diverse chemolithoautotrophic community and a new biogeochemical role for Thiomicrospira.

Sulfide mineral precipitation occurs at mid-ocean ridge (MOR) spreading centers, both in the form of plume particles and seafloor massive sulfide structures. A common constituent of MOR is the iron-bearing sulfide mineral pyrrhotite, which was chosen as a substrate for in-situ incubation studies in shallow waters of Catalina Island, CA to investigate the colonization of iron-oxidizing bacteria. Microbial community datasets were obtained from in-situ incubated pyrrhotite, allowing for direct comparison to microbial communities of iron-sulfides from active and inactive chimneys in deep-sea environments. Unclassified Gammaproteobacteria and Alphaproteobacteria (Magnetovibrio) largely dominated the bacterial community on pyrrhotite samples incubated in the water column while samples incubated at the surface sediment showed more even dominance by Deltaproteobacteria (Desulfobulbus), Gammaproteobacteria (Piscirickettsiaceae), Alphaproteobacteria (Rhodobacteraceae), and Bacteroidetes (Flavobacteriia). Cultivations that originated from pyrrhotite samples resulted in the enrichment of both, sheath-forming and stalk-forming Zetaproteobacteria. Additionally, a putative novel species of Thiomicrospira was isolated and shown to grow autotrophically with iron, indicating a new biogeochemical role for this ubiquitous microorganism.

New Insight into Microbial Iron Oxidation as Revealed by the Proteomic Profile of an Obligate Iron-Oxidizing Chemolithoautotroph.

Microaerophilic, neutrophilic, iron-oxidizing bacteria (FeOB) grow via the oxidation of reduced Fe(II) at or near neutral pH, in the presence of oxygen, making them relevant in numerous environments with elevated Fe(II) concentrations. However, the biochemical mechanisms for Fe(II) oxidation by these neutrophilic FeOB are unknown, and genetic markers for this process are unavailable. In the ocean, microaerophilic microorganisms in the genus Mariprofundus of the class Zetaproteobacteria are the only organisms known to chemolithoautotrophically oxidize Fe and concurrently biomineralize it in the form of twisted stalks of iron oxyhydroxides. The aim of this study was to identify highly expressed proteins associated with the electron transport chain of microaerophilic, neutrophilic FeOB. To this end, Mariprofundus ferrooxydans PV-1 was cultivated, and its proteins were extracted, assayed for redox activity, and analyzed via liquid chromatography-tandem mass spectrometry for identification of peptides. The results indicate that a cytochrome c4, cbb3-type cytochrome oxidase subunits, and an outer membrane cytochrome c were among the most highly expressed proteins and suggest an involvement in the process of aerobic, neutrophilic bacterial Fe oxidation. Proteins associated with alternative complex III, phosphate transport, carbon fixation, and biofilm formation were abundant, consistent with the lifestyle of Mariprofundus.

Clinical and histopathological features of a thymolipoma in a dog.

This study presents a case of a canine thymolipoma, which is a rare, slow-growing, benign tumor of the thymus composed of mature adipose tissue and thymic tissue. A 9-year-old spayed, female miniature pinscher presented with chronic cough and dyspnoea. Radiology revealed pleural effusion and a mediastinal mass with a fatty appearance. The mass was attached to, and silhouetted, the adjacent pericardium. Microscopically, the mass was composed of adipose tissue with numerous cords and nests of thymic tissue without corticomedullary arrangement. To the authors' knowledge, this is the first description of this uncommon neoplasm in a dog. The gross and histological findings are similar to those described for thymolipomas in humans. The possible histogenesis for this neoplasia in a dog is also discussed.