Human cytomegalovirus degrades DMXL1 to inhibit autophagy, lysosomal acidification, and viral assembly

Human cytomegalovirus (HCMV) is an important human pathogen that regulates host immunity and hijacks host compartments, including lysosomes, to assemble virions. We combined a quantitative proteomic analysis of HCMV infection with a database of proteins involved in vacuolar acidification, revealing Dmx-like protein-1 (DMXL1) as the only protein that acidifies vacuoles yet is degraded by HCMV. Systematic comparison of viral deletion mutants reveals the uncharacterized 7 kDa US33A protein as necessary and sufficient for DMXL1 degradation, which occurs via recruitment of the E3 ubiquitin ligase Kip1 ubiquitination-promoting complex (KPC). US33A-mediated DMXL1 degradation inhibits lysosome acidification and autophagic cargo degradation. Formation of the virion assembly compartment, which requires lysosomes, occurs significantly later with US33A-expressing virus infection, with reduced viral replication. These data thus identify a viral strategy for cellular remodeling, with the potential to employ US33A in therapies for viral infection or rheumatic conditions, in which inhibition of lysosome acidification can attenuate disease.

An extremely energetic cosmic ray observed by a surface detector array

Cosmic rays are energetic charged particles from extraterrestrial sources, with the highest-energy events thought to come from extragalactic sources. Their arrival is infrequent, so detection requires instruments with large collecting areas. In this work, we report the detection of an extremely energetic particle recorded by the surface detector array of the Telescope Array experiment. We calculate the particle's energy as [Formula: see text] (~40 joules). Its arrival direction points back to a void in the large-scale structure of the Universe. Possible explanations include a large deflection by the foreground magnetic field, an unidentified source in the local extragalactic neighborhood, or an incomplete knowledge of particle physics.

ADAM17 targeting by human cytomegalovirus remodels the cell surface proteome to simultaneously regulate multiple immune pathways

Human cytomegalovirus (HCMV) is a major human pathogen whose life-long persistence is enabled by its remarkable capacity to systematically subvert host immune defenses. In exploring the finding that HCMV infection up-regulates tumor necrosis factor receptor 2 (TNFR2), a ligand for the pro-inflammatory antiviral cytokine TNFα, we found that the underlying mechanism was due to targeting of the protease, A Disintegrin And Metalloproteinase 17 (ADAM17). ADAM17 is the prototype 'sheddase', a family of proteases that cleaves other membrane-bound proteins to release biologically active ectodomains into the supernatant. HCMV impaired ADAM17 surface expression through the action of two virally-encoded proteins in its UL/b' region, UL148 and UL148D. Proteomic plasma membrane profiling of cells infected with an HCMV double-deletion mutant for UL148 and UL148D with restored ADAM17 expression, combined with ADAM17 functional blockade, showed that HCMV stabilized the surface expression of 114 proteins (P < 0.05) in an ADAM17-dependent fashion. These included reported substrates of ADAM17 with established immunological functions such as TNFR2 and jagged1, but also numerous unreported host and viral targets, such as nectin1, UL8, and UL144. Regulation of TNFα-induced cytokine responses and NK inhibition during HCMV infection were dependent on this impairment of ADAM17. We therefore identify a viral immunoregulatory mechanism in which targeting a single sheddase enables broad regulation of multiple critical surface receptors, revealing a paradigm for viral-encoded immunomodulation.

Proteomic analysis of circulating immune cells identifies cellular phenotypes associated with COVID-19 severity

Certain serum proteins, including C-reactive protein (CRP) and D-dimer, have prognostic value in patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Nonetheless, these factors are non-specific, providing limited mechanistic insight into the peripheral blood mononuclear cell (PBMC) populations that drive the pathogenesis of severe COVID-19. To identify cellular phenotypes associated with disease, we performed a comprehensive, unbiased analysis of total and plasma-membrane PBMC proteomes from 40 unvaccinated individuals with SARS-CoV-2, spanning the whole disease spectrum. Combined with RNA sequencing (RNA-seq) and flow cytometry from the same donors, we define a comprehensive multi-omic profile for each severity level, revealing that immune-cell dysregulation progresses with increasing disease. The cell-surface proteins CEACAMs1, 6, and 8, CD177, CD63, and CD89 are strongly associated with severe COVID-19, corresponding to the emergence of atypical CD3+CD4+CEACAM1/6/8+CD177+CD63+CD89+ and CD16+CEACAM1/6/8+ mononuclear cells. Utilization of these markers may facilitate real-time patient assessment by flow cytometry and identify immune populations that could be targeted to ameliorate immunopathology.

Tumor Embolization through Meningohypophyseal and Inferolateral Trunks is Safe and Effective

BACKGROUND AND PURPOSE

Skull base tumors are commonly supplied by dural branches of the meningohypophyseal and inferolateral trunks. Embolization through these arteries is often avoided due to technical challenges and inherent risks; however, successful embolization can be a valuable surgical adjunct. We aimed to review the success and complications in our series of tumor embolizations through the meningohypophyseal and inferolateral trunks.

MATERIALS AND METHODS

We performed a retrospective review of patients with tumor treated with preoperative embolization at our institution between 2010 and 2020. We reviewed the following data: patients' demographics, tumor characteristics, endovascular embolization variables, and surgical results including estimated blood loss, the need for transfusion, and operative time.

RESULTS

Among 155 tumor embolization cases, we identified 14 patients in whom tumor embolization was performed using the meningohypophyseal (n = 13) or inferolateral (n = 4) trunk. In this group of patients, on average, 79% of tumors were embolized. No mortality or morbidity from the embolization procedure was observed in this subgroup of patients. The average estimated blood loss in the operation was 395 mL (range, 200-750 mL). None of the patients required a transfusion, and the average operative time was 7.3 hours.

CONCLUSIONS

Some skull base tumors necessitate embolization through ICA branches such as the meningohypophyseal and inferolateral trunks. Our series demonstrates that an effective and safe embolization may be performed through these routes.

Comparative Cell Surface Proteomic Analysis of the Primary Human T Cell and Monocyte Responses to Type I Interferon

The cellular response to interferon (IFN) is essential for antiviral immunity, IFN-based therapy and IFN-related disease. The plasma membrane (PM) provides a critical interface between the cell and its environment, and is the initial portal of entry for viruses. Nonetheless, the effect of IFN on PM proteins is surprisingly poorly understood, and has not been systematically investigated in primary immune cells. Here, we use multiplexed proteomics to quantify IFNα2a-stimulated PM protein changes in primary human CD14+ monocytes and CD4+ T cells from five donors, quantifying 606 and 482 PM proteins respectively. Comparison of cell surface proteomes revealed a remarkable invariance between donors in the overall composition of the cell surface from each cell type, but a marked donor-to-donor variability in the effects of IFNα2a. Furthermore, whereas only 2.7% of quantified proteins were consistently upregulated by IFNα2a at the surface of CD4+ T cells, 6.8% of proteins were consistently upregulated in primary monocytes, suggesting that the magnitude of the IFNα2a response varies according to cell type. Among these differentially regulated proteins, we found the viral target Endothelin-converting enzyme 1 (ECE1) to be an IFNα2a-stimulated protein exclusively upregulated at the surface of CD4+ T cells. We therefore provide a comprehensive map of the cell surface of IFNα2a-stimulated primary human immune cells, including previously uncharacterized interferon stimulated genes (ISGs) and candidate antiviral factors.

Killer cell proteases can target viral immediate-early proteins to control human cytomegalovirus infection in a noncytotoxic manner

Human cytomegalovirus (HCMV) is the most frequent viral cause of congenital defects and can trigger devastating disease in immune-suppressed patients. Cytotoxic lymphocytes (CD8⁺ T cells and NK cells) control HCMV infection by releasing interferon-γ and five granzymes (GrA, GrB, GrH, GrK, GrM), which are believed to kill infected host cells through cleavage of intracellular death substrates. However, it has recently been demonstrated that the in vivo killing capacity of cytotoxic T cells is limited and multiple T cell hits are required to kill a single virus-infected cell. This raises the question whether cytotoxic lymphocytes can use granzymes to control HCMV infection in a noncytotoxic manner. Here, we demonstrate that (primary) cytotoxic lymphocytes can block HCMV dissemination independent of host cell death, and interferon-α/β/γ. Prior to killing, cytotoxic lymphocytes induce the degradation of viral immediate-early (IE) proteins IE1 and IE2 in HCMV-infected cells. Intriguingly, both IE1 and/or IE2 are directly proteolyzed by all human granzymes, with GrB and GrM being most efficient. GrB and GrM cleave IE1 after Asp³⁹⁸ and Leu⁴¹⁴, respectively, likely resulting in IE1 aberrant cellular localization, IE1 instability, and functional impairment of IE1 to interfere with the JAK-STAT signaling pathway. Furthermore, GrB and GrM cleave IE2 after Asp¹⁸⁴ and Leu¹⁷³, respectively, resulting in IE2 aberrant cellular localization and functional abolishment of IE2 to transactivate the HCMV UL112 early promoter. Taken together, our data indicate that cytotoxic lymphocytes can also employ noncytotoxic ways to control HCMV infection, which may be explained by granzyme-mediated targeting of indispensable viral proteins during lytic infection.

Human cytomegalovirus (HCMV) is the leading viral cause of congenital defects, can trigger disease in immune-compromised patients, and plays roles in cancer development. Cytotoxic lymphocytes kill HCMV-infected cells via releasing a set of five cytotoxic serine proteases called granzymes. However, the killing capacity of cytotoxic cells is limited and multiple T cell hits are required to kill a single virus-infected cell. This raises the question whether cytotoxic lymphocytes can use granzymes to control HCMV infection in a noncytotoxic manner. Here, we show that cytotoxic lymphocytes can also use granzymes to inhibit HCMV replication in absence of cell death. All five granzymes cleave and inactivate both viral immediate-early (IE1/2) proteins, which are essential players for initiating HCMV infection. Our data support the model that cytotoxic cells employ granzymes to dampen HCMV replication prior to accumulation of sufficient hits to kill the infected cell.

Identifying critical source areas using multiple methods for effective diffuse pollution mitigation

Diffuse pollution from agriculture constitutes a key pressure on the water quality of freshwaters and is frequently the cause of ecological degradation. The problem of diffuse pollution can be conceptualised with a source-mobilisation-pathway (or delivery)-impact model, whereby the combination of high source risk and strong connected pathways leads to 'critical source areas' (CSAs). These areas are where most diffuse pollution will originate, and hence are the optimal places to implement mitigation measures. However, identifying the locations of these areas is a key problem across different spatial scales within catchments. A number of approaches are frequently used for this assessment, although comparisons of these assessments are rarely carried out. We evaluate the CSAs identified via traditional walkover surveys supported by three different approaches, highlighting their benefits and disadvantages. These include a custom designed smartphone app; a desktop geographic information system (GIS) and terrain analysis-based SCIMAP (Sensitive Catchment Integrated Modelling and Analysis Platform) approach; and the use of a high spatial resolution drone dataset as an improved input data for SCIMAP modelling. Each of these methods captures the locations of the CSAs, revealing similarities and differences in the prioritisation of CSA features. The differences are due to the temporal and spatial resolution of the three methods such as the use of static land cover information, the ability to capture small scale features, such as gateways and the incomplete catchment coverage of the walkover survey. The relative costs and output resolutions of the three methods indicate that they are suitable for application at different catchment scales in conjunction with other methods. Based on the results in this paper, it is recommended that a multi-evidence-based approach to diffuse pollution management is taken across catchment spatial scales, incorporating local knowledge from the walkover with the different data resolutions of the SCIMAP approach.

Nuclear phosphorylated Dicer processes double-stranded RNA in response to DNA damage

The endoribonuclease Dicer is a key component of the human RNA interference pathway and is known for its role in cytoplasmic microRNA production. Recent findings suggest that noncanonical Dicer generates small noncoding RNA to mediate the DNA damage response (DDR). Here, we show that human Dicer is phosphorylated in the platform-Piwi/Argonaute/Zwille-connector helix cassette (S1016) upon induction of DNA damage. Phosphorylated Dicer (p-Dicer) accumulates in the nucleus and is recruited to DNA double-strand breaks. We further demonstrate that turnover of damage-induced nuclear, double-stranded (ds) RNA requires additional phosphorylation of carboxy-terminal Dicer residues (S1728 and S1852). DNA damage-induced nuclear Dicer accumulation is conserved in mammals. Dicer depletion causes endogenous DNA damage and delays the DDR by impaired recruitment of repair factors MDC1 and 53BP1. Collectively, we place Dicer within the context of the DDR by demonstrating a DNA damage-inducible phosphoswitch that causes localized processing of nuclear dsRNA by p-Dicer to promote DNA repair.

Purification and Biochemical Analysis of the Cytoplasmic Membrane from the Desiccation-Tolerant Cyanobacterium Nostoc commune UTEX 584

The cytoplasmic membrane of the heterocystous cyanobacterium Nostoc commune UTEX 584 was isolated free of thylakoids and phycobiliprotein-membrane complexes by flotation centrifugation. Purified membranes had a buoyant density of 1.07 g cm and were bright orange. Twelve major proteins were detected in the membrane, and of these, the most abundant had molecular masses of 83, 71, 68, 51, and 46 kilodaltons. The ester-linked fatty acids of the methanol fraction contained 16:0, 18:0, 18:1omega9c, 20:0, and 20:3omega3 with no traces of hydroxy fatty acids. Compound 20:3omega3 represented 56.8% of the total fatty acid methyl esters, a feature which distinguishes the cell membrane of N. commune UTEX 584 from those of all other cyanobacteria which have been characterized to date. Fatty acid 18:3 was not detected. Carotenoids were analyzed by highperformance liquid chromatography. The cytoplasmic membrane contained beta-carotene and echinenone as the dominant carotenoids and lacked chlorophyll a and pheophytin a. Whole cells contained beta-carotene and echinenone, and lesser amounts of zeaxanthin and (3R)-cryptoxanthin.

Avoidable maternal deaths: three ways to help now

The current paper examines the realities of women delivering in resource-poor settings, and recommends cost-effective, scalable strategies for making these deliveries safer. Ninety-five percent of maternal deaths occur in poor settings, and the largest proportion of these deaths are women who deliver at home, far away from health care facilities, and without financial access to skilled providers. This situation will improve only when policymakers and programme planners refocus their attention on service delivery and financing interventions, with the potential to reach the largest portion of women living in places where mortality is the highest. We suggest three feasible interventions that can potentially minimise both demand and supply side problems of safe delivery: (1) misoprostol to treat postpartum haemorrhage, an easy to use and heat stable technology to reduce the leading cause of maternal deaths; (2) alternative providers, such as clinical officers, trained to offer emergency obstetric care services; (3) financing safe delivery through vouchers or other mechanisms that can be implemented in poor settings and made attractive to the donor community through output-based assistance (OBA).

Prevention of postpartum hemorrhage: options for home births in rural Ethiopia

This paper sought to determine the safety and feasibility of home-based prophylaxis of postpartum hemorrhage (PPH) with misoprostol, including assessment of the need for referrals and additional interventions. In rural Tigray, Ethiopia, traditional birth attendants (TBAs) in intervention areas were trained to administer 600mcg of oral misoprostol. In non-intervention areas women were referred to the nearest health facility. Of the 966 vaginal deliveries attended by TBAs, only 8.9% of those who took misoprostol prophylactically (n = 485) needed additional intervention due to excessive bleeding compared to 18.9% of those who did not take misoprostol (n = 481).The experience of symptoms among those who used misoprostol can be considered of minor relevance and self-contained. This study found that prophylactic use of misoprostol in home births is a safe and feasible intervention. Community health care workers trained in its use can correctly and effectively administer misoprostol and be a champion in reducing PPH morbidity and mortality.

A novel method to estimate the aortic pressure waveform using B-mode ultrasound images acquired from a suprasternal view

A novel method to obtain the aortic pressure waveform using a sequence of B-mode images is developed in this project. An automatic edge detection algorithm is applied to a sequence of longitudinal images of the aortic arch acquired from a suprasternal view. The aortic distension waveform is obtained by measuring the distance between the two edges throughout the cardiac cycle. It is then calibrated using the systolic and diastolic pressures from the brachial artery to obtain an estimated pressure waveform. This method was applied to 5 healthy children, pulse pressure amplification and total arterial compliance were calculated from the estimated waveforms.

Future internet research and experimentation

The research community worldwide has increasingly drawn its attention to the weaknesses of the current Internet. Many proposals are addressing the perceived problems, ranging from new enhanced protocols to fix specific problems up to the most radical proposal to redesign and deploy a fully new Internet. Most of the problems in the current Internet are rooted in the tremendous pace of increase of its use. As a consequence there was little time to address the deficiencies of the Internet from an architectural point of view.

Within FP7, the European Commission has facilitated the creation of European expert groups around the theme FIRE "Future Internet Research and Experimentation". FIRE has two related dimensions: on one hand, promoting experimentally-driven long-term, visionary research on new paradigms and networking concepts and architectures for the future Internet; on the other hand, building a large-scale experimentation facility supporting both medium- and long-term research on networks and services by gradually federating existing and new testbeds for emerging or future Internet technologies. By addressing future challenges for the Internet such as mobility, scalability, security and privacy, this new experimentally-driven approach is challenging the mainstream perceptions for future Internet development. This new initiative is intended to complement the more industrially-driven approaches which are addressed under the FP7 Objective "The Network of the Future" within the FP7-ICT Workprogramme 2007-08. FIRE is focused on exploring new and radically better technological solutions for the future Internet, while preserving the "good" aspects of the current Internet, in terms of openness, freedom of expression and ubiquitous access. The FIRE activities are being launched in the 2nd ICT call, which closes in October 2007, under the FP7-ICT Objective 1.6 "New Paradigms and Experimental Facilities" (budget ε40m). Projects are envisaged to start in early 2008.

Misoprostol and active management of the third stage of labor

OBJECTIVE

To compare current practices for the active management of the third stage of labor (AMTSL) with the use of 600 mug of oral misoprostol.

METHODS

An operations research study was designed to compare blood loss with current AMTSL practices and misoprostol use.

RESULTS

Women in the misoprostol group were less likely to bleed 500 ml or more (adjusted odds ratio, 0.30; 95% confidence interval, 0.16-0.56) compared with those in the current practices group. In the current practices group 73% women required interventions because of postpartum hemorrhage, compared with 11% in the misoprostol group.

CONCLUSION

In situations where oxytocin and or ergometrine are not consistently and appropriately used during third stage of labor, misoprostol should be considered for inclusion in the AMTSL protocol.

Controlling postpartum hemorrhage after home births in Tanzania

OBJECTIVES

Determine safety of household management of postpartum hemorrhage (PPH) with 1000 microg of rectal misoprostol, and assess possible reduction in referrals and the need for additional interventions.

METHODS

Traditional birth attendants (TBAs) in Kigoma, Tanzania were trained to recognize PPH (500 ml of blood loss). Blood loss measurement was standardized by using a local garment, the "kanga". TBAs in the intervention area gave 1000 microg of misoprostol rectally when PPH occurred. Those in the non-intervention area referred the women to the nearest facility.

RESULTS

454 women in the intervention and 395 in the non-intervention areas were eligible. 111 in the intervention area and 73 in the non-intervention had PPH. Fewer than 2% of the PPH women in the intervention area were referred, compared with 19% in the non-intervention.

CONCLUSION

Misoprostol is a low cost, easy to use technology that can control PPH even without a medically trained attendant.

Does it matter that organ donors are not dead? Ethical and policy implications

The "standard position" on organ donation is that the donor must be dead in order for vital organs to be removed, a position with which we agree. Recently, Robert Truog and Walter Robinson have argued that (1) brain death is not death, and (2) even though "brain dead" patients are not dead, it is morally acceptable to remove vital organs from those patients. We accept and defend their claim that brain death is not death, and we argue against both the US "whole brain" criterion and the UK "brain stem" criterion. Then we answer their arguments in favour of removing vital organs from "brain dead" and other classes of comatose patients. We dispute their claim that the removal of vital organs is morally equivalent to "letting nature take its course", arguing that, unlike "allowing to die", it is the removal of vital organs that kills the patient, not his or her disease or injury. Then, we argue that removing vital organs from living patients is immoral and contrary to the nature of medical practice. Finally, we offer practical suggestions for changing public policy on organ transplantation.

Meeting the contraceptive and AIDS prevention needs of people living on a dollar a day

The new millennium sees the largest cohort of young people in history entering its fertile years. Many of these people are too poor to pay the full cost of modern contraception, but the money available for subsidizing their needs is exceedingly limited. The AIDS pandemic is placing additional, unprecedented demand on already overstretched resources. Existing methods of contraception that are well established and off-patent can be produced in bulk at low cost, and will remain the backbone of future programmes. The use of misoprostol as an abortifacient is likely to spread rapidly. New methods must take into account the limitations of the health infrastructure in developing countries and the imperative of low cost. Given the constraints of money, skills and facilities, it is essential to set realistic priorities for future contraceptive research and development. It is suggested that the greatest needs are for a woman-controlled method of preventing HIV transmission and for a non-surgical method of female sterilization.

Desiccation tolerance: a simple process?

Water is essential for life, and thus the removal of water from a cell is a severe, often lethal stress. This is not a remarkable observation but it is one that is often taken for granted. Desiccation-tolerant cells implement structural, physiological and molecular mechanisms to survive severe water deficit. These mechanisms, and the components and pathways which facilitate them, are poorly understood. Here, recent developments are considered to illustrate the importance of desiccation, longevity and cell stasis in basic microbiology, and the relevance of the topic to the metabolic engineering of sensitive cells, including those of humans.

A requiem for whole brain death: a response to D. Alan Shewmon's 'the brain and somatic integration'

Alan Shewmon's article, 'The brain and somatic integration: Insights into the standard biological rationale for equating "brain death" with death' (2001), strikes at the heart of the standard justification for whole brain death criteria. The standard justification, which I call the 'standard paradigm', holds that the permanent loss of the functions of the entire brain marks the end of the integrative unity of the body. In my response to Shewmon's article, I first offer a brief summary of the standard paradigm and cite recent work by advocates of whole brain criteria who tenaciously cling to the standard paradigm despite increasing evidence showing that it has significant weaknesses. Second, I address Shewmon's case against the standard paradigm, arguing that he is successful in showing that whole brain dead patients have integrated organic unity. Finally, I discuss some minor problems with Shewmon's article, along with suggestions for further elaboration.

Expression of intercellular adhesion molecule-1 in the cortex of preserved rat kidneys

BACKGROUND

Prolonged cold ischemia has been shown to be an important factor in the development of posttransplant renal dysfunction. The exact mechanisms have not been completely defined. The expression of intercellular adhesion molecule-1 (ICAM-1) (CD 54) in rat kidneys stored in University of Wisconsin (UW) solution was studied in an attempt to correlate ischemia time with immunogenicity of the graft.

METHODS

Kidneys from male Lewis rats were perfused with UW solution, removed, and bathed in UW solution at 4 degrees C for 4, 12, 24, and 48 h. For the evaluation of expression of ICAM-1, immunohistochemical staining, Western blotting, and semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) were performed.

RESULTS

Immunohistochemical staining in normal, nonischemic kidneys revealed that glomerular capillaries expressed ICAM-1 but that tubular cells did not. The preserved kidneys were analyzed by immunohistochemistry, Western blotting, and semiquantitative RT-PCR and showed increased transcription and expression of ICAM-1 in the cortex of the kidney. Expression reached a maximum at 24 h and declined at 48 h. The ICAM-1 protein expression in the preserved kidney cortex relative to control kidneys was increased at 4 h (1.68 +/- 0.60-fold of control kidneys, P = 0.06), 12 h (2.38 +/- 0.90-fold, P = 0.02), 24 h (3.70 +/- 1.29-fold, P = 0.01), and 48 h (2.00 +/- 0.54-fold, P = 0.01). The messenger RNA expression (the ratio of ICAM-1 to glyceraldehyde-3-phosphate dehydrogenase) in preserved kidneys cortex relative to control kidneys was increased at 4 h (1.19 +/- 0.14-fold of control kidneys), 12 h (1.38 +/- 0.16-fold), 24 h (1.77 +/- 0.29-fold), and 48 h (1.19 +/- 0.12-fold) (P < 0.05 for all time points).

CONCLUSIONS

We conclude that cold preservation of rat kidneys in UW solution induces increasing levels of ICAM-1 cell surface expression and gene transcription. Further study is necessary to determine if this increase in adhesion molecule expression increases the immunogenicity of the allograft and contributes to the development of posttransplant renal dysfunction.

Form species Nostoc commune (Cyanobacteria)

The form species concept for the Cyanobacteria was evaluated using a comprehensive set of Nostoc samples that were collected during the past two centuries, from all continents, including regions from the Tropics to the Poles. Phylogenies were constructed based upon the conserved regions of tRNALeu (UAA) group I intron DNA sequences. Thirty-four forms contained a tRNALeu (UAA) intron of 284 nt. These 284-nt introns contained 200 nt of conserved sequence that, in most cases, shared 100% sequence identity, they had three variable regions (I, II and III) amounting to 84 nt, contained no hypervariable region and formed a discrete cluster in phylogenetic analysis. These forms represented 31 independent populations in both hemispheres and constitute examples of form species Nostoc commune. Multiple introns were obtained from several of the populations. Ten populations contained introns of 287-340 nt with a hypervariable region, 8 to 59 nt in length, located between variable regions I and II. Alignments identified 15 examples where 5'-AAAAUCC-3' occurred at the hypervariable region-variable region II boundary; this sequence is identical to the conserved sequence at the 3' intron-exon boundary (splice site) within the tRNALeu (UAA) gene. The possibility that hypervariable regions were removed from the primary intron through secondary splicing was tested in vitro but proved to be negative under the experimental conditions used. Shared morphologies of genetically different strains, dissimilar morphologies in strains that share identical genetic markers, incorrect naming of culture collection strains and genetic drift in cultured strains emphasize that the successful delineation of cyanobacterial species requires the application of multiple taxonomic criteria.

Engineering mammalian cells for solid-state sensor applications

A fundamental advance in the development and application of cell- and tissue-based biosensors would be the ability to achieve air-dry stabilization of mammalian (especially human) cells with subsequent recovery following rehydration. The would allow for the preparation of sensors with extended shelf lives, only requiring the addition of water for activation. By understanding and subsequently employing the tactics used by desiccation-tolerant extremophiles, it may be possible to design stabilized mammalian cell-based biosensors. The approaches required to realize this goal are discussed and illustrated with several examples.

Gene transfer to the desiccation-tolerant cyanobacterium Chroococcidiopsis

The coccoid cyanobacterium Chroococcidiopsis dominates microbial communities in the most extreme arid hot and cold deserts. These communities withstand constraints that result from multiple cycles of drying and wetting and/or prolonged desiccation, through mechanisms which remain poorly understood. Here we describe the first system for genetic manipulation of Chroococcidiopsis. Plasmids pDUCA7 and pRL489, based on the pDU1 replicon of Nostoc sp. strain PCC 7524, were transferred to different isolates of Chroococcidiopsis via conjugation and electroporation. This report provides the first evidence that pDU1 replicons can be maintained in cyanobacteria other than Nostoc and Anabaena. Following conjugation, both plasmids replicated in Chroococcidiopsis sp. strains 029, 057, and 123 but not in strains 171 and 584. Both plasmids were electroporated into strains 029 and 123 but not into strains 057, 171, and 584. Expression of P(psbA)-luxAB on pRL489 was visualized through in vivo luminescence. Efficiencies of conjugative transfer for pDUCA7 and pRL489 into Chroococcidiopsis sp. strain 029 were approximately 10(-2) and 10(-4) transconjugants per recipient cell, respectively. Conjugative transfer occurred with a lower efficiency into strains 057 and 123. Electrotransformation efficiencies of about 10(-4) electrotransformants per recipient cell were achieved with strains 029 and 123, using either pDUCA7 or pRL489. Extracellular deoxyribonucleases were associated with each of the five strains. Phylogenetic analysis, based upon the V6 to V8 variable regions of 16S rRNA, suggests that desert strains 057, 123, 171, and 029 are distinct from the type species strain Chroococcidiopsis thermalis PCC 7203. The high efficiency of conjugative transfer of Chroococcidiopsis sp. strain 029, from the Negev Desert, Israel, makes this a suitable experimental strain for genetic studies on desiccation tolerance.