Nineteenth-Century American Literature and the Discourse of Natural History

Nineteenth-Century American Literature and the Discourse of Natural History illuminates how literary experimentation with natural history provides penumbral views of environmental survival. The book brings together feminist revisions of scientific objectivity and critical race theory on diaspora to show how biogeography influenced material and metaphorical concepts of species and race. It also highlights how lesser known writers of color like Simon Pokagon and James McCune Smith connected species migration and mutability to forms of racial uplift. The book situates these literary visions of environmental fragility and survival amidst the development of Darwinian theories of evolution and against a westward expanding American settler colonialism.

Experimental evolution of Vibrio cholerae: Identification of genes involved in motility in presence of polymyxin B

Vibrio cholerae is the bacteria responsible for the cholera disease and a natural inhabitant of aquatic environments. Biofilm formation is important for human colonization and environmental survival. Motility is essential for adhesion and biofilm formation by V. cholerae. In a previous study, we showed that motility and biofilm formation are altered in the presence of sub-inhibitory concentrations of polymyxin B in V. cholerae. In this study, we performed an experimental evolution to identify genes rescuing the motility in the presence of polymyxin B. Mutations in 5 genes have been identified: ihfA, vacJ (mlaA), mlaF, dacB and ccmH. The details of these mutations, their potential impact on the function of the proteins they encode and on the motility in presence of polymyxin B are discussed.

Polymicrobial Interactions Operative during Pathogen Transmission

ABSTRACT Pathogen transmission is a key point not only for infection control and public health interventions but also for understanding the selective pressures in pathogen evolution. The “success” of a pathogen lies not in its ability to cause signs and symptoms of illness but in its ability to be shed from the initial hosts, survive between hosts, and then establish infection in a new host. Recent insights have shown the importance of the interaction between the pathogen and both the commensal microbiome and coinfecting pathogens on shedding, environmental survival, and acquisition of infection. Pathogens have evolved in the context of cooperation and competition with other microbes, and the roles of these cooperations and competitions in transmission can inform novel preventative and therapeutic strategies. IMPORTANCE Transmission of pathogens from one host to another is an essential event in pathogenesis. Transmission is driven by factors intrinsic to the host and to the pathogen. In addition, transmission is altered by interactions of the pathogen with the commensal microbiota of the host and coinfecting pathogens. Recent insights into these interactions have shown both enhanced and reduced transmission efficiencies depending on the makeup of the polymicrobial community. This review will discuss polymicrobial interactions during shedding from the initial host, time in the environment, and acquisition by the new host.

Induction and Resuscitation of Viable but Nonculturable Corynebacterium diphtheriae

Many pathogenic bacteria, including Escherichia coli and Vibrio cholerae, can become viable but nonculturable (VBNC) following exposure to specific stress conditions. Corynebacterium diphtheriae, a known human pathogen causing diphtheria, has not previously been shown to enter the VBNC state. Here, we report that C. diphtheriae can become VBNC when exposed to low temperatures. Morphological differences in culturable and VBNC C. diphtheriae were examined using scanning electron microscopy. Culturable cells presented with a typical rod-shape, whereas VBNC cells showed a distorted shape with an expanded center. Cells could be transitioned from VBNC to culturable following treatment with catalase. This was further evaluated via RNA sequence-based transcriptomic analysis and reverse-transcription quantitative PCR of culturable, VBNC, and resuscitated VBNC cells following catalase treatment. As expected, many genes showed different behavior by resuscitation. The expression of both the diphtheria toxin and the repressor of diphtheria toxin genes remained largely unchanged under all four conditions (culturable, VBNC, VBNC after the addition of catalase, and resuscitated cells). This is the first study to demonstrate that C. diphtheriae can enter a VBNC state and that it can be rescued from this state via the addition of catalase. This study helps to expand our general understanding of VBNC, the pathogenicity of VBNC C. diphtheriae, and its environmental survival strategy.

Draft Genome Sequences of Eight Campylobacter volucris Isolates from Freshwater Sources in Victoria, Australia

ABSTRACT Campylobacter spp. can survive and be transmitted from a range of environments. Here, we examine eight draft genome sequences of Campylobacter volucris, identified as part of an examination of waterborne Campylobacter species. This is the first report of environmental survival of C. volucris outside gull species.

Siderophore piracy enhances Vibrio cholerae environmental survival and pathogenesis

Vibrio cholerae, the aetiological agent of cholera, possesses multiple iron acquisition systems, including those for the transport of siderophores. How these systems benefit V. cholerae in low-iron, polymicrobial communities in environmental settings or during infection remains poorly understood. Here, we demonstrate that in iron-limiting conditions, co-culture of V. cholerae with a number of individual siderophore-producing microbes significantly promoted V. cholerae growth in vitro. We further show that in the host environment with low iron, V. cholerae colonizes better in adult mice in the presence of the siderophore-producing commensal Escherichia coli . Taken together, our results suggest that in aquatic reservoirs or during infection, V. cholerae may overcome environmental and host iron restriction by hijacking siderophores from other microbes.