RESUMO

The human milk microbiota (HMM) of healthy women can vary substantially, as demonstrated by recent advances in DNA sequencing technology. However, the method used to extract genomic DNA (gDNA) from these samples may impact the observed variations and potentially bias the microbiological reconstruction. Therefore, it is important to use a DNA extraction method that is able to effectively isolate gDNA from a diverse range of microorganisms. In this study, we improved and compared a DNA extraction method for gDNA isolation from human milk (HM) samples to commercial and standard protocols. We evaluated the extracted gDNA using spectrophotometric measurements, gel electrophoresis, and PCR amplifications to assess its quantity, quality, and amplifiability. Additionally, we tested the improved method's ability to isolate amplifiable gDNA from fungi, Gram-positive and Gram-negative bacteria to validate its potential for reconstructing microbiological profiles. The improved DNA extraction method resulted in a higher quality and quantity of the extracted gDNA compared to the commercial and standard protocols and allowed for polymerase chain reaction (PCR) amplification of the V3-V4 regions of the 16S ribosomal gene in all the samples and the ITS-1 region of the fungal 18S ribosomal gene in 95% of the samples. These results suggest that the improved DNA extraction method demonstrates better performance for gDNA extraction from complex samples such as HM.

RESUMO

ABSTRACT Studies on public health and wild mammal biodiversity include a genetic component. For blood samples, there must be optimal sample collection conditions since these can affect DNA preservation and extraction. This study evaluated the use of liquid and dry DNA preservation methods and commercial and non-commercial DNA extraction methods on field-collected blood samples. For this, 264 total blood samples were collected from wild mammals. A first group of samples was preserved in guanidine hydrochloride (GuHCl) and DNA was extracted using six commercial kits: Bioline, Norgen, Invitrogen, Promega, and Qiagen, in addition to phenol-chloroform isoamyl alcohol (PC) and guanidine thiocyanate (GIT). Another group of samples was preserved in Whatman® FTA® cards and DNA was extracted with PC and GIT. The extractions with GIT and PC showed the highest values (ng/µL) and variation in DNA concentration, while the commercial kit showed low variation. Sample preservation in Whatman® FTA® cards provided low variation and quantity of the extracted DNA compared with the use of GuHCl. Concerning DNA quality, the commercial kits yielded higher purity, while GIT and PC-based protocols provided highly variable results. Furthermore, the use of GIT and PC yielded a higher amount of DNA, yet, of variable quality. Overall, extraction based on commercial kits and Whatman® FTA® preservation allowed obtaining more standardized DNA qualities and quantities.

RESUMEN Los estudios sobre salud pública y biodiversidad de mamíferos silvestres incluyen un componente genético. Para las muestras de sangre, se debe tener condiciones óptimas de colección, ya que pueden afectar la preservación y la extracción del ADN. Este estudio evaluó el uso de métodos de preservación de ADN líquido y seco y métodos de extracción de ADN comerciales y no comerciales, en muestras de sangre, recolectadas en campo. Para ello, se recogieron 264 muestras de sangre totales de mamíferos salvajes. Se preservó un primer grupo de muestras en clorhidrato de guanidina (GuHCl) y se extrajo el ADN, utilizando seis kits comerciales: Bioline, Norgen, Invitrogen, Promega y Qiagen, además de dos protocolos no comerciales: fenol-cloroformo isoamil alcohol (PC) y guanidina tiocianato (GIT). Otro grupo de muestras, se preservó en tarjetas Whatman® FTA® y se extrajo el ADN, con PC y GIT. Las extracciones con GIT y PC mostraron los valores y variaciones más altas en la concentración de ADN (ng/µL), mientras que el kit comercial mostró una baja variación. La preservación de la muestra en tarjetas Whatman® FTA® proporcionó una baja variación y cantidad de ADN extraído, en comparación con el uso de GuHCl. En cuanto a la calidad del ADN, los kits comerciales produjeron una mayor pureza (A260/280), mientras que los protocolos basados en GIT y PC proporcionaron resultados muy variables. Además, el uso de GIT y PC originó una mayor cantidad de ADN, pero de calidad variable. En general, la extracción basada en kits comerciales y la conservación Whatman® FTA® permitió obtener calidades y cantidades de ADN más estandarizadas.

RESUMO

DNA extraction methods were evaluated for the yield and purity of DNA recovered from mycorrhized roots and whether the recovered DNA is suitable for amplification of arbuscular mycorrhizal (AM) fungal SSU rDNA. The DNeasy Plant Mini Kit and three extraction buffers were used alone or in combination with either polyvinylpyrrolidone (PVP), polyvinylpolypyrrolidone (PVPP) and/or activated charcoal (AC). Among the extraction methods tested, those based on the CTAB buffers yielded more DNA than those based on the TE buffer and the DNeasy Plant Mini Kit. Moreover, the use of AC alone or in combination with PVPP reduced DNA yield, while it significantly improved the purity of recovered DNA, whatever the extraction buffer. On the other hand, the success of nested-PCR amplification was negatively correlated with the amount of template DNA and positively correlated with the purity of recovered DNA. Three methods based on the TE buffer, two on the CTAB-ßM buffer and one on the DNeasy Plant Mini Kit produced high-quality DNA in terms of purity and PCR performance. However, the TE buffer-based methods are less time consuming than the CTAB-ßM buffer-based methods, and cheaper than the method based on the DNeasy Plant Mini Kit.

Diferentes métodos de extração de ADN, a partir de amostras de raízes, foram testados e o ADN obtido foi avaliado para a amplificação de genes ribossomais de fungos micorrízicos arbusculares (AM). Três tampões de extração foram utilizados isoladamente ou em combinação com polivinilpirrolidona (PVP), polivinipolipirrolidona (PVPP) e/ou carvão ativado (CA), além do DNeasy Plant Mini Kit. Entre os métodos de extração testados, aqueles com base no tampão CTAB renderam mais ADN do que os baseados no tampão TE e o DNeasy Plant Mini Kit. A utilização de CA ou PVPP nos diferentes tampões reduziram o rendimento de ADN, contudo, melhoraram significativamente a pureza do ADN recuperado, independentemente do tampão de extração. Por outro lado, o sucesso da amplificação por Nested-PCR foi negativamente correlacionado com a quantidade de DNA molde, e positivamente correlacionada com a pureza do ADN. Três métodos baseados no tampão TE, dois no tampão CTAB-ßM e o DNeasy Plant Mini Kit produziram ADN de alta qualidade, em termos de pureza e rendimento da PCR. No entanto, os métodos baseados em tampão TE demandam menos tempo do que os métodos baseados em tampão CTAB-ßM e são mais baratos do que o uso do DNeasy Plant Mini Kit.

Assuntos

RESUMO

DNA extraction methods were evaluated for the yield and purity of DNA recovered from mycorrhized roots and whether the recovered DNA is suitable for amplification of arbuscular mycorrhizal (AM) fungal SSU rDNA. The DNeasy Plant Mini Kit and three extraction buffers were used alone or in combination with either polyvinylpyrrolidone (PVP), polyvinylpolypyrrolidone (PVPP) and/or activated charcoal (AC). Among the extraction methods tested, those based on the CTAB buffers yielded more DNA than those based on the TE buffer and the DNeasy Plant Mini Kit. Moreover, the use of AC alone or in combination with PVPP reduced DNA yield, while it significantly improved the purity of recovered DNA, whatever the extraction buffer. On the other hand, the success of nested-PCR amplification was negatively correlated with the amount of template DNA and positively correlated with the purity of recovered DNA. Three methods based on the TE buffer, two on the CTAB-M buffer and one on the DNeasy Plant Mini Kit produced high-quality DNA in terms of purity and PCR performance. However, the TE buffer-based methods are less time consuming than the CTAB-M buffer-based methods, and cheaper than the method based on the DNeasy Plant Mini Kit.(AU)

Diferentes métodos de extração de ADN, a partir de amostras de raízes, foram testados e o ADN obtido foi avaliado para a amplificação de genes ribossomais de fungos micorrízicos arbusculares (AM). Três tampões de extração foram utilizados isoladamente ou em combinação com polivinilpirrolidona (PVP), polivinipolipirrolidona (PVPP) e/ou carvão ativado (CA), além do DNeasy Plant Mini Kit. Entre os métodos de extração testados, aqueles com base no tampão CTAB renderam mais ADN do que os baseados no tampão TE e o DNeasy Plant Mini Kit. A utilização de CA ou PVPP nos diferentes tampões reduziram o rendimento de ADN, contudo, melhoraram significativamente a pureza do ADN recuperado, independentemente do tampão de extração. Por outro lado, o sucesso da amplificação por Nested-PCR foi negativamente correlacionado com a quantidade de DNA molde, e positivamente correlacionada com a pureza do ADN. Três métodos baseados no tampão TE, dois no tampão CTAB-M e o DNeasy Plant Mini Kit produziram ADN de alta qualidade, em termos de pureza e rendimento da PCR. No entanto, os métodos baseados em tampão TE demandam menos tempo do que os métodos baseados em tampão CTAB-M e são mais baratos do que o uso do DNeasy Plant Mini Kit.(AU)

Assuntos