Cases of Meningococcal Disease Associated with Travel to Saudi Arabia for Umrah Pilgrimage - United States, United Kingdom, and France, 2024.

Invasive meningococcal disease (IMD), caused by infection with the bacterium Neisseria meningitidis, usually manifests as meningitis or septicemia and can be severe and life-threatening (1). Six serogroups (A, B, C, W, X, and Y) account for most cases (2). N. meningitidis is transmitted person-to-person via respiratory droplets and oropharyngeal secretions. Asymptomatic persons can carry N. meningitidis and transmit the bacteria to others, potentially causing illness among susceptible persons. Outbreaks can occur in conjunction with large gatherings (3,4). Vaccines are available to prevent meningococcal disease. Antibiotic prophylaxis for close contacts of infected persons is critical to preventing secondary cases (2).

Expansion of Neisseria meningitidis Serogroup C Clonal Complex 10217 during Meningitis Outbreak, Burkina Faso, 2019.

During January 28-May 5, 2019, a meningitis outbreak caused by Neisseria meningitidis serogroup C (NmC) occurred in Burkina Faso. Demographic and laboratory data for meningitis cases were collected through national case-based surveillance. Cerebrospinal fluid was collected and tested by culture and real-time PCR. Among 301 suspected cases reported in 6 districts, N. meningitidis was the primary pathogen detected; 103 cases were serogroup C and 13 were serogroup X. Whole-genome sequencing revealed that 18 cerebrospinal fluid specimens tested positive for NmC sequence type (ST) 10217 within clonal complex 10217, an ST responsible for large epidemics in Niger and Nigeria. Expansion of NmC ST10217 into Burkina Faso, continued NmC outbreaks in the meningitis belt of Africa since 2019, and ongoing circulation of N. meningitidis serogroup X in the region underscore the urgent need to use multivalent conjugate vaccines in regional mass vaccination campaigns to reduce further spread of those serogroups.

Selection of Antibiotics as Prophylaxis for Close Contacts of Patients with Meningococcal Disease in Areas with Ciprofloxacin Resistance - United States, 2024.

Meningococcal disease, caused by the bacterium Neisseria meningitidis, is a rare but life-threatening illness that requires prompt antibiotic treatment for patients and antibiotic prophylaxis for their close contacts. Historically, N. meningitidis isolates in the United States have been largely susceptible to the antibiotics recommended for prophylaxis, including ciprofloxacin. Since 2019, however, the number of meningococcal disease cases caused by ciprofloxacin-resistant strains has increased. Antibiotic prophylaxis with ciprofloxacin in areas with ciprofloxacin resistance might result in prophylaxis failure. Health departments should preferentially consider using antibiotics other than ciprofloxacin as prophylaxis for close contacts when both of the following criteria have been met in a local catchment area during a rolling 12-month period: 1) the reporting of two or more invasive meningococcal disease cases caused by ciprofloxacin-resistant strains, and 2) ≥20% of all reported invasive meningococcal disease cases are caused by ciprofloxacin-resistant strains. Other than ciprofloxacin, alternative recommended antibiotic options include rifampin, ceftriaxone, or azithromycin. Ongoing monitoring for antibiotic resistance of meningococcal isolates through surveillance and health care providers' reporting of prophylaxis failures will guide future updates to prophylaxis considerations and recommendations.

Effects of 'Perinatal Risk Factors Associated with Hearing Loss' on Auditory Outcomes in Cochlear Implant Recipient Children.

Cochlear implantation (CI) is used for rehabilitation of children with bilateral severe to profound permanent childhood hearing loss (PCHL). Recently, treatment of such children has been influenced by diagnostic technological advances. Children with perinatal risk factors associated with PCHL can undergo CI. The primary aim of this study was to determine the effects of 'perinatal risk factor associated with PCHL' on post-CI auditory outcomes. In this prospective study at a tertiary care centre we evaluated 50 cochlear implanted children from October 2011 to March 2013. The case group consisted of 6 (12%) children who had presence of 'perinatal risk factor associated with PCHL' and control group consisted of 44 (88%) children without any 'perinatal risk factor associated with PCHL'. All patients received auditory and speech rehabilitation and we evaluated their auditory perception outcomes by categories of auditory performance (CAP) and meaningful auditory integration scale (MAIS) scores at 1 year post-CI. There were significantly decreased mean MAIS scores (decrease of 8.6%) and mean CAP scores (decrease of 6.7%) in CI recipient children with 'perinatal risk factor associated with PCHL' as compared to those who were without any 'perinatal risk factor associated with PCHL' at 1 year after CI. However, in children with 'perinatal risk factor associated with PCHL', mean CAP & MAIS scores (auditory perception outcomes) were still more than 80% of maximum achievable CAP & MAIS scores. In this study, CI recipient children who were without any 'perinatal risk factor associated with PCHL' had significantly better mean MAIS & CAP scores (auditory perception outcomes) 1 year post-CI. However, even in children who had 'perinatal risk factor associated with PCHL', there was substantial improvement in auditory perception outcomes at 1 year post-CI and CI was still helpful in these children. Hence, knowledge of 'perinatal risk factor associated with PCHL' can provide reasonable help in predicting the auditory perception outcome and optimal counselling of families of CI candidates.

Bacterial responses to background organic pollutants in the northeast subarctic Pacific Ocean.

Thousands of man-made synthetic chemicals are released to oceans and compose the anthropogenic dissolved organic carbon (ADOC). Little is known about the effects of this chronic pollution on marine microbiome activities. In this study, we measured the pollution level at three sites in the Northeast Subarctic Pacific Ocean (NESAP) and investigated how mixtures of three model families of ADOC at different environmentally relevant concentrations affected naturally occurring marine bacterioplankton communities' structure and metabolic functioning. The offshore northernmost site (North) had the lowest concentrations of hydrocarbons, as well as organophosphate ester plasticizers, contrasting with the two other continental shelf sites, the southern coastal site (South) being the most contaminated. At North, ADOC stimulated bacterial growth and promoted an increase in the contribution of some Gammaproteobacteria groups (e.g. Alteromonadales) to the 16 rRNA pool. These groups are described as fast responders after oil spills. In contrast, minor changes in South microbiome activities were observed. Gene expression profiles at Central showed the coexistence of ADOC degradation and stress-response strategies to cope with ADOC toxicities. These results show that marine microbial communities at three distinct domains in NESAP are influenced by background concentrations of ADOC, expanding previous assessments for polar and temperate waters.

Acquisition of Ciprofloxacin Resistance Among an Expanding Clade of ß-Lactamase-Positive, Serogroup Y Neisseria meningitidis in the United States.

BACKGROUND: Penicillin and ciprofloxacin are important for invasive meningococcal disease (IMD) management and prevention. IMD cases caused by penicillin- and ciprofloxacin-resistant Neisseria meningitidis containing a ROB-1 ß-lactamase gene (blaROB-1) and a mutated DNA gyrase gene (gyrA) have been recently reported in the United States. METHODS: We examined 2097 meningococcal genomes collected through US population-based surveillance from January 2011 to February 2020 to identify IMD cases caused by strains with blaROB-1- or gyrA-mediated resistance. Antimicrobial resistance was confirmed phenotypically. The US isolate genomes were compared to non-US isolate genomes containing blaROB-1. Interspecies transfer of ciprofloxacin resistance was assessed by comparing gyrA among Neisseria species. RESULTS: Eleven penicillin- and ciprofloxacin-resistant isolates were identified after December 2018; all were serogroup Y, sequence type 3587, clonal complex (CC) 23, and contained blaROB-1 and a T91I-containing gyrA allele. An additional 22 penicillin-resistant, blaROB-1- containing US isolates with wild-type gyrA were identified from 2013 to 2020. All 33 blaROB-1-containing isolates formed a single clade, along with 12 blaROB-1-containing isolates from 6 other countries. Two-thirds of blaROB-1-containing US isolates were from Hispanic individuals. Twelve additional ciprofloxacin-resistant isolates with gyrA T91 mutations were identified. Ciprofloxacin-resistant isolates belonged to 6 CCs and contained 10 unique gyrA alleles; 7 were similar or identical to alleles from Neisseria lactamica or Neisseria gonorrhoeae. CONCLUSIONS: Recent IMD cases caused by a dual resistant serogroup Y suggest changing antimicrobial resistance patterns in the United States. The emerging dual resistance is due to acquisition of ciprofloxacin resistance by ß-lactamase-containing N. meningitidis. Routine antimicrobial resistance surveillance will effectively monitor resistance changes and spread.

Genome Sequences and Metagenome-Assembled Genome Sequences of Microbial Communities Enriched on Phytoplankton Exometabolites.

We report 11 bacterial draft genome sequences and 38 metagenome-assembled genomes (MAGs) from marine phytoplankton exometabolite enrichments. The genomes and MAGs represent marine bacteria adapted to the metabolite environment of phycospheres, organic matter-rich regions surrounding phytoplankton cells, and are useful for exploring functional and taxonomic attributes of phytoplankton-associated bacterial communities.

Effects of Age at Cochlear Implantation on Auditory Outcomes in Cochlear Implant Recipient Children.

Cochlear implantation (CI) is used for rehabilitation of children with bilateral severe to profound sensorineural hearing loss. Recently, treatment of such children has been influenced by diagnostic technological advances. Infants and toddlers are now increasingly included for CI. The primary aim of this study was to determine the effects of 'age at CI' on CI outcome. The primary aim of this study was to determine the effects of 'age at CI' on CI outcome. In this prospective study at a tertiary care centre, we evaluated 50 cochlear implanted children from October 2011 to March 2013. The case group consists of 15 (30%) children who underwent CI at more than 5 years of age and control group consisted of 35 (70%) children who underwent CI at less than or equal to 5 years age. All patients received auditory and speech rehabilitation and we evaluated their auditory perception outcomes 1 year post CI, the children were assessed by categories of auditory performance (CAP) and meaningful auditory integration scale (MAIS) tests. There were significantly improved mean auditory perception outcomes (increase of 12.29% in CAP, and 14.05% in MAIS scores) at 1 year post CI in CI recipients of age group '5 years or less' in comparison to those who underwent CI at 'more than 5 years of age'. However, children of 'more than 5 years' age at CI, mean CAP and MAIS scores were still more than 80% of maximum achievable CAP and MAIS scores. In this study, CI recipient children who were implanted at less than or equal to 5 years of age were found to have significantly improved auditory perception outcome at 1 year post CI. Hence, it appears preferable to provide CI early. However, even in children who underwent CI at more than 5 years of age, there was substantial improvement in auditory perception outcomes and CI was still helpful in these children. Hence, knowledge of 'age at CI' can provide reasonable help in predicting the auditory perception outcome and optimal counselling of families of CI candidates.

Sulfur metabolites that facilitate oceanic phytoplankton-bacteria carbon flux.

Unlike biologically available nitrogen and phosphorus, which are often at limiting concentrations in surface seawater, sulfur in the form of sulfate is plentiful and not considered to constrain marine microbial activity. Nonetheless, in a model system in which a marine bacterium obtains all of its carbon from co-cultured phytoplankton, bacterial gene expression suggests that at least seven dissolved organic sulfur (DOS) metabolites support bacterial heterotrophy. These labile exometabolites of marine dinoflagellates and diatoms include taurine, N-acetyltaurine, isethionate, choline-O-sulfate, cysteate, 2,3-dihydroxypropane-1-sulfonate (DHPS), and dimethylsulfoniopropionate (DMSP). Leveraging from the compounds identified in this model system, we assessed the role of sulfur metabolites in the ocean carbon cycle by mining the Tara Oceans dataset for diagnostic genes. In the 1.4 million bacterial genome equivalents surveyed, estimates of the frequency of genomes harboring the capability for DOS metabolite utilization ranged broadly, from only 1 out of every 190 genomes (for the C2 sulfonate isethionate) to 1 out of every 5 (for the sulfonium compound DMSP). Bacteria able to participate in DOS transformations are dominated by Alphaproteobacteria in the surface ocean, but by SAR324, Acidimicrobiia, and Gammaproteobacteria at mesopelagic depths, where the capability for utilization occurs in higher frequency than in surface bacteria for more than half the sulfur metabolites. The discovery of an abundant and diverse suite of marine bacteria with the genetic capacity for DOS transformation argues for an important role for sulfur metabolites in the pelagic ocean carbon cycle.

Identifying labile DOM components in a coastal ocean through depleted bacterial transcripts and chemical signals.

Understanding which compounds comprising the complex and dynamic marine dissolved organic matter (DOM) pool are important in supporting heterotrophic bacterial production remains a major challenge. We eliminated sources of labile phytoplankton products, advected terrestrial material and photodegradation products to coastal microbial communities by enclosing water samples in situ for 24 h in the dark. Bacterial genes for which expression decreased between the beginning and end of the incubation and chemical formulae that were depleted over this same time frame were used as indicators of bioavailable compounds, an approach that avoids augmenting or modifying the natural DOM pool. Transport- and metabolism-related genes whose relative expression decreased implicated osmolytes, carboxylic acids, fatty acids, sugars and organic sulfur compounds as candidate bioreactive molecules. FT-ICR MS analysis of depleted molecular formulae implicated functional groups ~ 30-40 Da in size cleaved from semi-polar components of DOM as bioreactive components. Both gene expression and FT-ICR MS analyses indicated higher lability of compounds with sulfur and nitrogen heteroatoms. Untargeted methodologies able to integrate biological and chemical perspectives can be effective strategies for characterizing the labile microbial metabolites participating in carbon flux.

Impact of socioeconomic factors on paediatric cochlear implant outcomes.

OBJECTIVES: The study was aimed at evaluating the impact of certain socioeconomic factors such as family income, level of parents' education, distance between the child's home and auditory verbal therapy clinic, and age of the child at implantation on postoperative cochlear implant outcomes. METHODS: Children suffering from congenital bilateral profound sensorineural hearing loss and a chronologic age of 4 years or younger at the time of implantation were included in the study. Children who were able to complete a prescribed period of a 1-year follow-up were included in the study. These children underwent cochlear implantation surgery, and their postoperative outcomes were measured and documented using categories of auditory perception (CAP), meaningful auditory integration (MAIS), and speech intelligibility rating (SIR) scores. Children were divided into three groups based on the level of parental education, family income, and distance of their home from the rehabilitation-- auditory verbal therapy clinic. RESULTS: A total of 180 children were studied. The age at implantation had a significant impact on the postoperative outcomes, with an inverse correlation. The younger the child's age at the time of implantation, the better were the postoperative outcomes. However, there were no significant differences among the CAP, MAIS, and SIR scores and each of the three subgroups. Children from families with an annual income of less than $7,500, between $7,500 and $15,000, and more than $15,000 performed equally well, except for significantly higher SIR scores in children with family incomes more than $15,000. Children with of parents who had attended high school or possessed a bachelor's or Master's master's degree had similar scores, with no significant difference. Also, distance from the auditory verbal therapy clinic failed to have any significantimpact on a child's performance. DISCUSSION: These results have been variable, similar to those of previously published studies. A few of the earlier studies concurred with our results, but most of the studies had suggested that children in families of higher socioeconomic status had have better speech and language acquisition. CONCLUSIONS: Cochlear implantation significantly improves auditory perception and speech intelligibility of children suffering from profound sensorineural hearing loss. Younger The younger the age at implantation, the better are the results. Hence, early implantation should be promoted and encouraged. Our study suggests that children who followed the designated program of postoperative mapping and auditory verbal therapy for a minimum period of 1 year seemed to do equally well in terms of hearing perception and speech intelligibility, irrespective of the socioeconomic status of the family. Further studies are essential to assess the impact of these factors on long-term speech acquisition andlanguage development.

Recognition cascade and metabolite transfer in a marine bacteria-phytoplankton model system.

The trophic linkage between marine bacteria and phytoplankton in the surface ocean is a key step in the global carbon cycle, with almost half of marine primary production transformed by heterotrophic bacterioplankton within hours to weeks of fixation. Early studies conceptualized this link as the passive addition and removal of organic compounds from a shared seawater reservoir. Here, we analysed transcript and intracellular metabolite patterns in a two-member model system and found that the presence of a heterotrophic bacterium induced a potential recognition cascade in a marine phytoplankton species that parallels better-understood vascular plant response systems. Bacterium Ruegeria pomeroyi DSS-3 triggered differential expression of >80 genes in diatom Thalassiosira pseudonana CCMP1335 that are homologs to those used by plants to recognize external stimuli, including proteins putatively involved in leucine-rich repeat recognition activity, second messenger production and protein kinase cascades. Co-cultured diatoms also downregulated lipid biosynthesis genes and upregulated chitin metabolism genes. From differential expression of bacterial transporter systems, we hypothesize that nine diatom metabolites supported the majority of bacterial growth, among them sulfonates, sugar derivatives and organic nitrogen compounds. Similar recognition responses and metabolic linkages as observed in this model system may influence carbon transformations by ocean plankton.

Salvaging cochlear implant after wound infection: Well worth a try.

BACKGROUND: Cochlear implant (CI)-related wound infections are known to happen even years after the implant procedure and present a challenging clinical situation. Due to the formation of biofilm on the implant surface such infections are difficult to eradicate. Invariably explantation of the device is required for wound healing. METHOD: A 10-year-old patient presented with recurrent CI-related wound infection 8 years after implantation. The implant was salvaged with wound debridement and treating it with tea tree oil which is known for its biofilm eradicating properties. It was then covered with double layer of vascularised soft tissue. Combination of intravenous vancomycin and oral rifampicin known for their efficacy in biofilm-related infection was also used. RESULTS: The implant could be salvaged using this novel technique of treating the implant with a biofilm eradicating agent, wound debridement, double layer vascularised soft tissue cover, and long-term antibiotics. CONCLUSION: Agents having anti-biofilm activity when used in conjunction with surgical debridement and judicious antimicrobial therapy can be used for salvaging the implant and limiting the morbidity associated with these infections.

Expression patterns of elemental cycling genes in the Amazon River Plume.

Metatranscriptomics and metagenomics data sets benchmarked with internal standards were used to characterize the expression patterns for biogeochemically relevant bacterial and archaeal genes mediating carbon, nitrogen, phosphorus and sulfur uptake and metabolism through the salinity gradient of the Amazon River Plume. The genes were identified in 48 metatranscriptomic and metagenomic data sets summing to >500 million quality-controlled reads from six locations in the plume ecosystem. The ratio of transcripts per gene copy (a direct measure of expression made possible by internal standard additions) showed that the free-living bacteria and archaea exhibited only small changes in the expression levels of biogeochemically relevant genes through the salinity and nutrient zones of the plume. In contrast, the expression levels of genes in particle-associated cells varied over orders of magnitude among the stations, with the largest differences measured for genes mediating aspects of nitrogen cycling (nifH, amtB and amoA) and phosphorus acquisition (pstC, phoX and phoU). Taxa varied in their baseline gene expression levels and extent of regulation, and most of the spatial variation in the expression level could be attributed to changes in gene regulation after removing the effect of shifting taxonomic composition. We hypothesize that changes in microbial element cycling along the Amazon River Plume are largely driven by shifting activities of particle-associated cells, with most activities peaking in the mesohaline regions where N2 fixation rates are elevated.

Patterns of Transcript Abundance of Eukaryotic Biogeochemically-Relevant Genes in the Amazon River Plume.

The Amazon River has the largest discharge of all rivers on Earth, and its complex plume system fuels a wide array of biogeochemical processes, across a large area of the western tropical North Atlantic. The plume thus stimulates microbial processes affecting carbon sequestration and nutrient cycles at a global scale. Chromosomal gene expression patterns of the 2.0 to 156 µm size-fraction eukaryotic microbial community were investigated in the Amazon River Plume, generating a robust dataset (more than 100 million mRNA sequences) that depicts the metabolic capabilities and interactions among the eukaryotic microbes. Combining classical oceanographic field measurements with metatranscriptomics yielded characterization of the hydrographic conditions simultaneous with a quantification of transcriptional activity and identity of the community. We highlight the patterns of eukaryotic gene expression for 31 biogeochemically significant gene targets hypothesized to be valuable within forecasting models. An advantage to this targeted approach is that the database of reference sequences used to identify the target genes was selectively constructed and highly curated optimizing taxonomic coverage, throughput, and the accuracy of annotations. A coastal diatom bloom highly expressed nitrate transporters and carbonic anhydrase presumably to support high growth rates and enhance uptake of low levels of dissolved nitrate and CO2. Diatom-diazotroph association (DDA: diatoms with nitrogen fixing symbionts) blooms were common when surface salinity was mesohaline and dissolved nitrate concentrations were below detection, and hence did not show evidence of nitrate utilization, suggesting they relied on ammonium transporters to aquire recently fixed nitrogen. These DDA blooms in the outer plume had rapid turnover of the photosystem D1 protein presumably caused by photodegradation under increased light penetration in clearer waters, and increased expression of silicon transporters as silicon became limiting. Expression of these genes, including carbonic anhydrase and transporters for nitrate and phosphate, were found to reflect the physiological status and biogeochemistry of river plume environments. These relatively stable patterns of eukaryotic transcript abundance occurred over modest spatiotemporal scales, with similarity observed in sample duplicates collected up to 2.45 km in space and 120 minutes in time. These results confirm the use of metatranscriptomics as a valuable tool to understand and predict microbial community function.

Use of Intrathecal Fluorescein in Recurrent Meningitis after Cochlear Implantation.

INTRODUCTION: Congenital anomalies of the cochlea and labyrinth can be associated with meningitis and varying degrees of hearing loss or deafness. Despite antibiotics, meningitis remains a life threatening complication. CASE REPORT: We report a case of recurrent meningitis following episodes of otitis media in a cochlear implantee child with bilateral vestibulocochlear malformation, due to fistula in the stapes footplate. Intrathecal fluorescin was used to identify the leak site. CONCLUSION: Recurrent meningitis can indicate for possible immunological or anatomical abnormalities as well for chronic parameningeal infections. Intraoperative use of intrathecal fluorescin is an ideal investigative tool to demonstrate cerebrospinal fluid (CSF) leak site in patients in whom other investigations fail to do so.

Metagenomic and metatranscriptomic inventories of the lower Amazon River, May 2011.

BACKGROUND: The Amazon River runs nearly 6500 km across the South American continent before emptying into the western tropical North Atlantic Ocean. In terms of both volume and watershed area, it is the world's largest riverine system, affecting elemental cycling on a global scale. RESULTS: A quantitative inventory of genes and transcripts benchmarked with internal standards was obtained at five stations in the lower Amazon River during May 2011. At each station, metagenomes and metatranscriptomes were obtained in duplicate for two microbial size fractions (free-living, 0.2 to 2.0 µm; particle-associated, 2.0 to 297 µm) using 150 × 150 paired-end Illumina sequencing. Forty eight sample datasets were obtained, averaging 15 × 10(6) potential protein-encoding reads each (730 × 10(6) total). Prokaryotic metagenomes and metatranscriptomes were dominated by members of the phyla Actinobacteria, Planctomycetes, Betaproteobacteria, Verrucomicrobia, Nitrospirae, and Acidobacteria. The actinobacterium SCGC AAA027-L06 reference genome recruited the greatest number of reads overall, with this single bin contributing an average of 50 billion genes and 500 million transcripts per liter of river water. Several dominant taxa were unevenly distributed between the free-living and particle-associated size fractions, such as a particle-associated bias for reads binning to planctomycete Schlesneria paludicola and a free-living bias for actinobacterium SCGC AAA027-L06. Gene expression ratios (transcripts to gene copy ratio) increased downstream from Óbidos to Macapá and Belém, indicating higher per cell activity of Amazon River bacteria and archaea as river water approached the ocean. CONCLUSION: This inventory of riverine microbial genes and transcripts, benchmarked with internal standards for full quantitation, provides an unparalleled window into microbial taxa and functions in the globally important Amazon River ecosystem.

Cryptic carbon and sulfur cycling between surface ocean plankton.

About half the carbon fixed by phytoplankton in the ocean is taken up and metabolized by marine bacteria, a transfer that is mediated through the seawater dissolved organic carbon (DOC) pool. The chemical complexity of marine DOC, along with a poor understanding of which compounds form the basis of trophic interactions between bacteria and phytoplankton, have impeded efforts to identify key currencies of this carbon cycle link. Here, we used transcriptional patterns in a bacterial-diatom model system based on vitamin B12 auxotrophy as a sensitive assay for metabolite exchange between marine plankton. The most highly up-regulated genes (up to 374-fold) by a marine Roseobacter clade bacterium when cocultured with the diatom Thalassiosira pseudonana were those encoding the transport and catabolism of 2,3-dihydroxypropane-1-sulfonate (DHPS). This compound has no currently recognized role in the marine microbial food web. As the genes for DHPS catabolism have limited distribution among bacterial taxa, T. pseudonana may use this sulfonate for targeted feeding of beneficial associates. Indeed, DHPS was both a major component of the T. pseudonana cytosol and an abundant microbial metabolite in a diatom bloom in the eastern North Pacific Ocean. Moreover, transcript analysis of the North Pacific samples provided evidence of DHPS catabolism by Roseobacter populations. Other such biogeochemically important metabolites may be common in the ocean but difficult to discriminate against the complex chemical background of seawater. Bacterial transformation of this diatom-derived sulfonate represents a previously unidentified and likely sizeable link in both the marine carbon and sulfur cycles.

Bromodeoxyuridine labelling and fluorescence-activated cell sorting of polyamine-transforming bacterioplankton in coastal seawater.

Polyamines (PAs) are a group of nitrogen-rich dissolved organic nitrogen (DON) compounds that are ubiquitously distributed in marine environments. To identify bacteria that are involved in PA transformations, coastal bacterioplankton microcosms were amended with a single PA model compound, i.e. putrescine (PUT) or spermidine (SPD), or with no addition as controls (CTRs). Bromodeoxyuridine (BrdU) was added to all the microcosms to label newly synthesized DNAs. Fluorescence-activated cell sorting (FACS) analysis indicated significant increases in numbers of total cells and cells with both high and low levels of BrdU incorporation in the PUT and SPD microcosms, but not in the CTRs. 16S rDNA pyrotag sequencing of FACS-sorted cells indicated that PUT- and SPD-transforming bacteria were composed similarly of a diverse group of taxa affiliated with Actinobacteria, Bacteroidetes, Firmicutes and Proteobacteria (especially Roseobacter of its alpha lineage). Broad taxonomic distribution of PA-transforming bacteria was also indicated by the abundance and distribution of PA transporter gene homologues in a survey of sequenced marine bacterial genomes. Our results suggest that PAs may be common DON substrates for marine bacterioplankton, in line with the hypothesis that bacterially mediated PA transformation accounts for an important proportion of marine DON flux.