Fagos de bactérias redutoras de sulfato em água de produção de um reservatório de petróleo offshore: método tentativo de concentração e purificação / Phages of Sulphate Reducing Bacteria in reactor water from offshore oil wells: tentative method for concentration and purification

RESUMO O controle do crescimento microbiano é um desafio crescente na produção de petróleo e gás, uma vez que a presença de determinadas bactérias traz impactos econômica e ambientalmente negativos. As bactérias redutoras de sulfato (BRS) são particularmente problemáticas, uma vez que são responsáveis pela corrosão biológica ligada à produção de sulfeto de hidrogênio, efeito conhecido como souring. A principal forma de controle das BRS atualmente é a injeção de biocidas, no entanto essa estratégia, além de requerer aplicação contínua, tem se revelado pouco efetiva na eliminação de biofilmes e é associada a um alto risco de contaminação das águas. Portanto, é necessário que se busquem abordagens mais eficientes e específicas em relação ao controle microbiológico. O uso de vírus bacteriófagos vem ao encontro dessas necessidades, pois eles, após se multiplicarem, geralmente provocam a lise celular, liberando novas partículas virais e evitando que a bactéria se prolifere. Diante disso, este estudo propõe estabelecer um método para a concentração e a determinação da eficiência de recuperação de bacteriófagos de BRS presentes em água de reator oriunda de poços de petróleo. As amostras foram coletadas de dois reatores operados em batelada alimentada e que simulam um poço de petróleo. As amostras de água de reator foram primeiramente clarificadas, os vírus eluídos desse sedimento e, em seguida, concentrados por ultracentrifugação. O concentrado viral foi então purificado com Vertrel XF. Ensaios de semeadura experimental de miofago P1 nas amostras de água do reator revelaram taxa de recuperação viral de 27,7%, contra ao 16% obtidos com outros protocolos.

ABSTRACT The control of microbial growth is an increasing challenge in the production of oil and gas, since the presence of certain bacteria has economic and environmental negative impacts. Sulphate reducing bacteria are particularly problematic, since they are responsible for the biological corrosion associated with the production of hydrogen sulfide, an effect known as souring. The main form of control is the use of biocides; however, this strategy, in addition to requiring continuous application, has proven to be ineffective in the elimination of biofilms and is associated with a high risk of water contamination. Therefore, it is necessary to seek more efficient and specific approaches to microbiological control. The use of bacteriophage viruses meets these needs, because after they multiply, they usually cause cell lysis, releasing new viral particles and preventing the bacteria from proliferating. In view of this, this study proposes to establish a method for the concentration and detection of bacteriophages of Sulphate Reducing Bacteria present in reactor water from oil wells. The samples were collected from two reactors, operated in a batch fed to simulate an oil well. The reactor water samples were first clarified, viruses adsorbed to sediment were eluted and then concentrated by ultracentrifugation. The viral concentrate was then purified with Vertrel-XF. Experimental seeding of P1 myophage in water samples from the reactor revealed a viral recovery rate of 27.7%, compared to the 16% obtained by use of other protocols.

Identification of circo-like virus-Brazil genomic sequences in raw sewage from the metropolitan area of São Paulo: evidence of circulation two and three years after the first detection

BACKGROUND Two novel viruses named circo-like virus-Brazil (CLV-BR) hs1 and hs2 were previously discovered in a Brazilian human fecal sample through metagenomics. CLV-BR hs1 and hs2 possess a small circular DNA genome encoding a replication initiator protein (Rep), and the two genomes exhibit 92% nucleotide identity with each other. Phylogenetic analysis based on the Rep protein showed that CLV-BRs do not cluster with circoviruses, nanoviruses, geminiviruses or cycloviruses. OBJECTIVE The aim of this study was to search for CLV-BR genomes in sewage and reclaimed water samples from the metropolitan area of São Paulo, Brazil, to verify whether the first detection of these viruses was an isolated finding. METHODS Sewage and reclaimed water samples collected concomitantly during the years 2005-2006 were purified and concentrated using methodologies designed for the study of viruses. A total of 177 treated reclaimed water samples were grouped into five pools, as were 177 treated raw sewage samples. Nucleic acid extraction, polymerase chain reaction (PCR) amplification and Sanger sequencing were then performed.e FINDINGS CLV-BR genomes were detected in two pools of sewage samples, p6 and p9. Approximately 28% and 51% of the CLV-BR genome was amplified from p6 and p9, respectively, including 76% of the Rep gene. The detected genomes are most likely related to CLV-BR hs1. Comparative analysis showed several synonymous substitutions within Rep-encoding sequences, suggesting purifying selection for this gene, as has been observed for other eukaryotic circular Rep-encoding single-stranded DNA (CRESS-DNA) viruses. MAIN CONCLUSION The results therefore indicated that CLV-BR has continued to circulate in Brazil two and three years after first being detected.

Infection kinetics of human adenovirus serotype 41 in HEK 293 cells

The purpose of this work was to acquire an overview of the infectious cycle of HAdV-41 in permissive HEK 293 cells and compare it to that observed with the prototype of the genus, Human adenovirus C HAdV-2. HEK 293 cells were infected with each virus separately and were harvested every 12 h for seven days. Infection kinetics were analysed using confocal and electronic microscopy. The results show that, when properly cultivated, HAdV-41 was not fastidious. It had a longer multiplication cycle, which resulted in the release of complete viral particles and viral stocks reached high titres. After 60 h of infection, the export of viral proteins from the infected cell to the extracellular milieu was observed, with a pattern similar to that previously described for HAdV-2 penton-base trafficking after 30 h of infection. HAdV-41 had a non-lytic cycle and the infection spread from the first infected cell to its neighbours. The release process of the viral particles is unknown. The results observed for HAdV-41 infection in HEK 293 cells show how different this virus is from the prototype HAdV-2 and provides information for the development of this vector for use in gene therapy.

Longitudinal study on occurrence of adenoviruses and hepatitis A virus in raw domestic sewage in the city of Limeira, São Paulo / Estudo longitudinal da ocorrência de adenovírus e vírus da hepatite A em esgoto doméstico na cidade de Limeira, SP

The aim of this study was to verify the presence and annual distribution of adenoviruses and hepatitis A virus in domestic sewage in the city of Limeira, São Paulo. Fifty samples with a volume of 8 liters each were collected weekly from December 2004 to December 2005. The viruses were concentrated by filtration through positively charged ZP60S filter membranes, followed by ultracentrifugation. Human adenoviruses (HAdV) were detected by PCR followed by nested-PCR and screening for species F was done by restriction of the PCR product with TaqI endonuclease. Virus infectivity assays were performed by inoculation of concentrates onto HEp-2 cell monolayers. RT-PCR was used for the detection of hepatitis A virus. HAdV were detected in all samples, and 64% of samples were positive for infectious virus. Species F was present in 82% of the samples. Hepatitis A virus was detected in 48% of the samples. These results demonstrate that HAdV and HAV were present in the domestic sewage of Limeira throughout the period of study, demonstrating the importance of an adequate treatment before the disposal in the environment.

O objetivo do estudo foi verificar a ocorrência e a distribuição anual de adenovírus humanos e vírus da Hepatite A (VHA) no efluente doméstico da cidade de Limeira, São Paulo, ao longo do período de Dezembro de 2004 e Dezembro de 2005, com vistas à futura implementação de sistemas de tratmento de água de esgoto. Cinquenta amostras de efluente bruto com volume de 8L cada foram colhidas semanalmente e os vírus concentrados por filtração em membrana eletropositiva ZP60S, seguida de ultracentrifugação. Adenovírus foram detectados por PCR e nested-PCR. Adenovírus da espécie F foram distinguidos das demais por restrição do produto da PCR com endonuclease TaqI. Ensaios de infectividade viral foram realizados em culturas de células HEp-2. A presença do vírus da hepatite A também foi pesquisada nas mesmas amostras, fazendo-se uso de método de RT-PCR. Adenovírus foram detectados em todas as amostras, sendo a espécie F identificada em 82% destas. Sessenta e quatro por cento dos adenovírus detectados ainda estavam infecciosos. O vírus da Hepatite A foi detectado em 48% das amostras examinadas. Estes resultados evidenciam a presença e a circulação de Adenovírus humano e VHA nas águas de esgoto doméstico de Limeira ao longo do período de estudo, demonstrando a importância de um tratamento adequado desse material antes da disposição no meio ambiente.