Rosanna A Alegado

Publications (7) View all

• Article: Algoriphagus machipongonensis sp. nov. co-isolated with a colonial choanoflagellate.

  Rosanna A Alegado, Jonathan D Grabenstatter, Richard Zuzow, Andrea Morris, Sherri Y Huang, Roger E Summons, Nicole King
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  ABSTRACT: A Gram-negative, non-motile, non-spore-forming bacterial strain, PR1T, was isolated from a mud core sample containing colonial choanoflagellates near Hog Island, Virginia, USA and its taxonomic position was investigated. Strain PR1T grew optimally at 30°C in the presence of 3% (w/v) NaCl. Strain PR1T contained MK-7 as the major menaquinone as well as carotenoids but lacked pigments of the flexirubin-type. The predominant fatty acids were iso-C15:0 (29.4%), iso-C17:1 ω9c (18.5%), and summed feature 3 (C16:1 ω6c and/or C16:1 ω7c; 11.3%). The major polar lipids detected in strain PR1T were phosphatidylethanolamine as well as other phospholipids, aminophospholipids, and lipids of unknown character. The DNA G+C content was 38.7% mol. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain PR1T fell within the clade comprising Algoriphagus species, clustering with Algoriphagus halophilus JC 2051T (95.4% sequence similarity) and Algoriphagus lutimaris S1-3T (95.3% sequence similarity). The 16S rRNA gene sequence similarity between strain PR1T and the type strains of other Algoriphagus species were in the range of 91-95%. Differential phenotypic properties and phylogenetic and genetic distinctiveness of strain PR1T demonstrated that this strain was distinct from other Algoriphagus species, including its closest relative, A. halophilus. Based on phenotypic, chemotaxonomic, phylogenetic and genomic data, strain PR1T should be placed into the genus Algoriphagus as a novel species, for which the name Algoriphagus machipongonensis sp. nov. is proposed. The type strain is PR1T (= ATCC BAA-2233 T = DSM 24695 T).
  INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY 02/2012; · 2.11 Impact Factor
• Article: A bacterial sulfonolipid triggers multicellular development in the closest living relatives of animals.

  Rosanna A Alegado, Laura W Brown, Shugeng Cao, Renee K Dermenjian, Richard Zuzow, Stephen R Fairclough, Jon Clardy, Nicole King
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  ABSTRACT: Bacterially-produced small molecules exert profound influences on animal health, morphogenesis, and evolution through poorly understood mechanisms. In one of the closest living relatives of animals, the choanoflagellate Salpingoeca rosetta, we find that rosette colony development is induced by the prey bacterium Algoriphagus machipongonensis and its close relatives in the Bacteroidetes phylum. Here we show that a rosette inducing factor (RIF-1) produced by A. machipongonensis belongs to the small class of sulfonolipids, obscure relatives of the better known sphingolipids that play important roles in signal transmission in plants, animals, and fungi. RIF-1 has extraordinary potency (femtomolar, or 10(-15) M) and S. rosetta can respond to it over a broad dynamic range-nine orders of magnitude. This study provides a prototypical example of bacterial sulfonolipids triggering eukaryotic morphogenesis and suggests molecular mechanisms through which bacteria may have contributed to the evolution of animals.DOI:http://dx.doi.org/10.7554/eLife.00013.001.
  eLife. 01/2012; 1:e00013.
• Article: The two-component sensor kinase KdpD is required for Salmonella typhimurium colonization of Caenorhabditis elegans and survival in macrophages.

  Rosanna A Alegado, Chui-Yoke Chin, Denise M Monack, Man-Wah Tan
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  ABSTRACT: The ability of enteric pathogens to perceive and adapt to distinct environments within the metazoan intestinal tract is critical for pathogenesis; however, the preponderance of interactions between microbe- and host-derived factors remain to be fully understood. Salmonella enterica serovar Typhimurium is a medically important enteric bacterium that colonizes, proliferates and persists in the intestinal lumen of the nematode Caenorhabditis elegans. Several Salmonella virulence factors important in murine and tissue culture models also contribute to worm mortality and intestinal persistence. For example, PhoP and the virulence plasmid pSLT are virulence factors required for resistance to the C. elegans antimicrobial peptide SPP-1. To uncover additional determinants required for Salmonella typhimurium pathogenesis in vivo, we devised a genetic screen to identify bacterial mutants defective in establishing a persistent infection in the intestine of C. elegans. Here we report on identification of 14 loci required for persistence in the C. elegans intestine and characterization of KdpD, a sensor kinase of a two-component system in S. typhimurium pathogenesis. We show that kdpD mutants are profoundly attenuated in intestinal persistence in the nematode and in macrophage survival. These findings may be attributed to the essential role KdpD plays in promoting resistance to osmotic, oxidative and antimicrobial stresses.
  Cellular Microbiology 07/2011; 13(10):1618-37. · 5.46 Impact Factor
• Article: Cell differentiation and morphogenesis in the colony-forming choanoflagellate Salpingoeca rosetta.

  Mark J Dayel, Rosanna A Alegado, Stephen R Fairclough, Tera C Levin, Scott A Nichols, Kent McDonald, Nicole King
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  ABSTRACT: It has been posited that animal development evolved from pre-existing mechanisms for regulating cell differentiation in the single celled and colonial ancestors of animals. Although the progenitors of animals cannot be studied directly, insights into their cell biology may be gleaned from comparisons between animals and their closest living relatives, the choanoflagellates. We report here on the life history, cell differentiation and intercellular interactions in the colony-forming choanoflagellate Salpingoeca rosetta. In response to diverse environmental cues, S. rosetta differentiates into at least five distinct cell types, including three solitary cell types (slow swimmers, fast swimmers, and thecate cells) and two colonial forms (rosettes and chains). Electron microscopy reveals that cells within colonies are held together by a combination of fine intercellular bridges, a shared extracellular matrix, and filopodia. In addition, we have discovered that the carbohydrate-binding protein wheat germ agglutinin specifically stains colonies and the slow swimmers from which they form, showing that molecular differentiation precedes multicellular development. Together, these results help establish S. rosetta as a model system for studying simple multicellularity in choanoflagellates and provide an experimental framework for investigating the origin of animal multicellularity and development.
  Developmental Biology 06/2011; 357(1):73-82. · 4.07 Impact Factor
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  Article: Complete genome sequence of Algoriphagus sp. PR1, bacterial prey of a colony-forming choanoflagellate.

  Rosanna A Alegado, Steven Ferriera, Chad Nusbaum, Sarah K Young, Qian Zeng, Alma Imamovic, Stephen R Fairclough, Nicole King
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  ABSTRACT: Bacteria are the primary food source of choanoflagellates, the closest known relatives of animals. Studying signaling interactions between the Gram-negative Bacteroidetes bacterium Algoriphagus sp. PR1 and its predator, the choanoflagellate Salpingoeca rosetta, provides a promising avenue for testing hypotheses regarding the involvement of bacteria in animal evolution. Here we announce the complete genome sequence of Algoriphagus sp. PR1 and initial findings from its annotation.
  Journal of bacteriology 12/2010; 193(6):1485-6. · 3.94 Impact Factor