Characterization of the Achromobactin Iron Acquisition Operon in Sodalis glossinidius

Smith, Caitlin; Weiss, Brian L.; Aksoy, Serap; Runyen-Janecky, Laura J.

doi:10.1128/aem.03959-12

Cited by 21 publications

(19 citation statements)

References 41 publications

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“…We tried insertions at four different locations in dnaK using Targetron mutagenesis, as well as deletion of dnaK by allelic change. Notably, these mutagenesis techniques have been successfully used to make mutations in numerous other Sodalis genes (53–55). As Sodalis transitions from a free-living lifestyle to a mutualistic one (33), growth outside the tsetse host (on agar plates or in liquid BHI) may generate low-grade oxidative stress that requires DnaK for an appropriate cellular response that is critical for bacterial survival.…”

Section: Discussionmentioning

confidence: 99%

Thermal stress responses of Sodalis glossinidius, an indigenous bacterial symbiont of hematophagous tsetse flies

Roma

D’Souza

Somers

et al. 2019

Preprint

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Tsetse flies (Diptera: Glossinidae) house a taxonomically diverse microbiota that includes environmentally acquired bacteria, maternally transmitted symbiotic bacteria, and pathogenic African trypanosomes. Sodalis glossinidius, which is a facultative symbiont that resides intra and extracellularly within multiple tsetse tissues, has been implicated as a mediator of trypanosome infection establishment in the fly’s gut. Tsetse’s gut-associated population of Sodalis are subjected to marked temperature fluctuations each time their ectothermic fly host imbibes vertebrate blood. The molecular mechanisms that Sodalis employs to deal with this heat stress are unknown. In this study, we examined the thermal tolerance and heat shock response of Sodalis. When grown on BHI agar plates, the bacterium exhibited the most prolific growth at 25°C, and did not grow at temperatures above 30°C. Growth on BHI agar plates at 31°C was dependent on either the addition of blood to the agar or reduction in oxygen levels. Sodalis was viable in liquid cultures for 24 hours at 30°C, but began to die upon further exposure. The rate of death increased with increased temperature. Similarly, Sodalis was able to survive for 48 hours within tsetse flies housed at 30°C, while a higher temperature (37°C) was lethal. Sodalis’ genome contains homologues of the heat shock chaperone protein-encoding genes dnaK, dnaJ, and grpE, and their expression was up-regulated in thermally stressed Sodalis, both in vitro and in vivo within tsetse flies. Arrested growth of E. coli dnaK, dnaJ, or grpE mutants under thermal stress was reversed when the cells were transformed with a low copy plasmid that encoded the Sodalis homologues of these genes. The information contained in this study provides insight into how arthropod vector enteric commensals, many of which mediate their host’s ability to transmit pathogens, mitigate heat shock associated with the ingestion of a blood meal.AUTHOR SUMMARYMicroorganisms associated with insects must cope with fluctuating temperatures. Because symbiotic bacteria influence the biology of their host, how they respond to temperature changes will have an impact on the host and other microorganisms in the host. The tsetse fly and its symbionts represent an important model system for studying thermal tolerance because the fly feeds exclusively on vertebrate blood and is thus exposed to dramatic temperature shifts. Tsetse flies house a microbial community that can consist of symbiotic and environmentally acquired bacteria, viruses, and parasitic African trypanosomes. This work, which makes use of tsetse’s commensal symbiont, Sodalis glossinidius, is significance because it represents the only examination of thermal tolerance mechanisms in a bacterium that resides indigenously within an arthropod disease vector. A better understanding of the biology of thermal tolerance in Sodalis provides insight into thermal stress survival in other insect symbionts and may yield information to help control vector-borne disease.

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Section: Discussionmentioning

confidence: 99%

Thermal stress responses of Sodalis glossinidius, an indigenous bacterial symbiont of hematophagous tsetse flies

Roma

D’Souza

Somers

et al. 2019

Preprint

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“…Because tsetse flies are hematophagous insects, heme found in hemoglobin is likely to be the major iron source for Sodalis in the fly midgut. Interestingly, Sodalis mutants that fail to make the achromobactin siderophore, which is this bacterium's other major iron acquisition system, are still able to proliferate in the tsetse gut, likely because HemR is still present (15).…”

Section: Discussionmentioning

confidence: 99%

“…The expression of Sodalis siderophore synthesis genes is regulated by iron levels (15). To determine whether such regulation occurs with hemR, we used semiquantitative RT-PCR to measure expression levels of Sodalis hemR in cells grown under high-or low-iron conditions by using an iron chelator, EDDA.…”

Section: Expression Of Sodalis Hemr Is Repressed In a High-iron Envirmentioning

confidence: 99%

“…Sodalis produces several putative iron ac-quisition systems, including a previously characterized plasmidcarried (pSG1) mechanism that synthesizes and transports the iron-capturing siderophore achromobactin (15). Additionally, three Sodalis genes (hemT, hemU, and hemV) are homologous to well-characterized high-affinity ABC transport systems that transport heme through the inner membrane in other bacteria (15)(16)(17)(18)(19)(20), and Sodalis contains a putative gene (hemR) that may encode an outer membrane heme receptor. Finally, the tonB gene is present in Sodalis.…”

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confidence: 99%

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TonB-Dependent Heme Iron Acquisition in the Tsetse Fly Symbiont Sodalis glossinidius

Hrusa

Farmer

Weiss

et al. 2015

Appl Environ Microbiol

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bSodalis glossinidius is an intra-and extracellular symbiont of the tsetse fly (Glossina sp.), which feeds exclusively on vertebrate blood. S. glossinidius resides in a wide variety of tsetse tissues and may encounter environments that differ dramatically in iron content. The Sodalis chromosome encodes a putative TonB-dependent outer membrane heme transporter (HemR) and a putative periplasmic/inner membrane ABC heme permease system (HemTUV). Because these gene products mediate iron acquisition processes by other enteric bacteria, we characterized their regulation and physiological role in the Sodalis/tsetse system. Our results show that the hemR and tonB genes are expressed by S. glossinidius in the tsetse fly. Furthermore, transcription of hemR in Sodalis is repressed in a high-iron environment by the iron-responsive transcriptional regulator Fur. Expression of the S. glossinidius hemR and hemTUV genes in an Escherichia coli strain unable to use heme as an iron source stimulated growth in the presence of heme or hemoglobin as the sole iron source. This stimulation was dependent on the presence of either the E. coli or Sodalis tonB gene. Sodalis tonB and hemR mutant strains were defective in their ability to colonize the gut of tsetse flies that lacked endogenous symbionts, while wild-type S. glossinidius proliferated in this same environment. Finally, we show that the Sodalis HemR protein is localized to the bacterial membrane and appears to bind hemin. Collectively, this study provides strong evidence that TonB-dependent, HemR-mediated iron acquisition is important for the maintenance of symbiont homeostasis in the tsetse fly, and it provides evidence for the expression of bacterial high-affinity iron acquisition genes in insect symbionts.A ll insects house endogenous microorganisms that mediate critical aspects of their host's physiology. Tsetse flies (Diptera: Glossinidae) harbor three phylogenetically distinct endosymbiotic bacteria, including parasitic Wolbachia spp., obligate Wigglesworthia sp., and commensal Sodalis glossinidius, that are maternally transmitted during the fly's unique viviparous mode of reproduction (reviewed in references 1 and 2). Sodalis glossinidius, a Gram-negative gammaproteobacterium in the family Enterobacteriaceae, resides both intra-and extracellularly in a wide range of tsetse tissues, including the midgut, muscle, fat body, milk gland (a gland that supplies nutrients to developing intrauterine larvae), and salivary glands. Genomic data indicate that genes whose products facilitate a free-living lifestyle, such as those involved in the biosynthesis and transport of nutrients, are retained in Sodalis. However, the high number of pseudogenes (972) present in the S. glossinidius genome suggests that this bacterium is actively transitioning from a free-living to symbiotic lifestyle (3). Sodalis can be cultured outside its tsetse host, suggesting that it has not undergone a high degree of reductive evolution characteristic of ancient obligate bacterial symbioses. The ability to cul...

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“…Retargeted introns have been used in various species of the genera Agrobacterium [ 142 ], Azospirillum [ 148 ], Bacillus [ 149 ], Clostridium [ 145 ], Ehrlichia [ 150 ], Escherichia [ 105 ], Francisella [ 146 ], Lactococcus [ 151 ], Listeria [ 152 ], Paenibacillus [ 153 ], Pasteurella [ 154 ], Proteus [ 155 ], Pseudomonas [ 142 ], Ralstonia [ 143 ], Salmonella [ 111 ], Shewanella [ 156 ], Shigella [ 111 ], Sinorhizobium [ 139 ], Sodalis [ 157 ], Staphylococcus [ 144 ], Vibrio [ 158 ], and Yersinia [ 159 ]. In bacteria, targetrons are used primarily to obtain knockout mutants.…”

Section: Use Of Group II Introns In Biotechnologymentioning

confidence: 99%

Intron Biology, Focusing on Group II Introns, the Ancestors of Spliceosomal Introns

Molina-Sánchez

Nisa-Martínez

García-Rodríguez

et al. 2015

Genomic Elements in Health, Disease and Evolution

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Group II intron s are mobile metalloribozymes that self-splice from precursor RNA to generate excised intron lariat RNA forms, which invade new DNA genomic locations by reverse splicing . These retroelements also encode a reverse transcriptase that stabilizes the RNA structure for forward and reverse splicing and fi nally converts the inserted intron RNA back to DNA. For these reasons, group II introns initially identifi ed in the mitochondrial and chloroplast genomes of lower eukaryotes and plants, and subsequently found in bacteria and archaea are thought to be the ancestors of nuclear spliceosomal introns and non-long terminal repeat (non-LTR) retrotransposons [ 1 -4 ]. Recently identifi ed structural and functional similarities between group II introns and spliceosomal nuclear RNAs have suggested that group II introns may have played an important role at the very start of eukaryote evolution. It is now thought that their invasion of pre-eukaryotic genomes and their proliferation in those genomes may have driven the evolutionary separation of nucleus and cytoplasm [ 5 ].Typically, group II introns consist of a conserved RNA structure organized into six domains. Domain V is the most conserved of these domains and is considered to be an

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Characterization of the Achromobactin Iron Acquisition Operon in Sodalis glossinidius

Cited by 21 publications

References 41 publications

Thermal stress responses of Sodalis glossinidius, an indigenous bacterial symbiont of hematophagous tsetse flies

Thermal stress responses of Sodalis glossinidius, an indigenous bacterial symbiont of hematophagous tsetse flies

TonB-Dependent Heme Iron Acquisition in the Tsetse Fly Symbiont Sodalis glossinidius

Intron Biology, Focusing on Group II Introns, the Ancestors of Spliceosomal Introns

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