Assessment of bacteria and archaea in metalworking fluids using massive parallel 16S rRNA gene tag sequencing

Abstract

Significance and Impact of the Study: Water-miscible metalworking fluids provide a suitable base of life for micro-organisms, mainly bacteria and fungi. Earlier publications suggested that the diversity is rather low, but these studies were largely based on heterotrophic plate counts. This might have resulted in underestimation of population density and microbial diversity as some organisms might just refuse to grow. This study used high-throughput sequencing in the absence and presence of propidium monoazide to explore bacterial and archaeal presence in metalworking fluids. We established that diversity is low and bacterial populations are dominated by the genus Pseudomonas spp. AbstractDetermination of the bacterial diversity in industry-based liquid in-use watermiscible metalworking fluid (MWF) samples was targeted by massive parallel multiplex DNA sequencing, either directly or upon pretreatment with propidium monoazide (PMA) that allows differentiation between intact and physically damaged cells. As MWFs provide a suitable basis of life for microorganisms, the majority is preserved by biocides. 'Bio-concept' fluids on the other hand are bactericide free, which intentionally leads to substantial bacterial populations. Samples from both fluid types were chosen: A median of 51 operational taxonomic units at genera level (OTUs) were detected per sample, but only 13 were present at or above 1Á0% of the total population in any PMA-treated sample analysed. As both fluid types were mainly dominated by Pseudomonas spp., we resolved this genus on the species level and found the Pseudomonas oleovorans/pseudoalcaligenes group to predominate. We also looked for archaea and detected Methanobrevibacter spp., albeit in <3% of all samples analysed.

Selection and assembly of indigenous bacteria and methanogens from spent metalworking fluids and their potential as a starting culture in a fluidized bed reactor

“…Interestingly, Di Maiuta et al . () used parallel ribosomal gene tag sequencing and found Archaea in two of 78 samples analysed. All reads were classified into the genus of Methanobrevibacter spp.…”

“…Few studies have examined MWF for the presence of anaerobic bacteria (Van der Gast et al ., ; Bakalova et al ., ; Di Maiuta et al . ). Recently, Di Maiuta et al .…”

“…Recently, Di Maiuta et al . () used parallel ribosomal gene tag sequencing to profile microbes from industry‐based liquid in water‐miscible MWF samples. Archaeal DNA was only found in two of 78 samples analysed.…”

“…These studies were focused on the presence of aerobic bacteria. Few studies have examined MWF for the presence of anaerobic bacteria (Van der Gast et al, 2001;Bakalova et al, 2007;Di Maiuta et al 2017). Recently, Di Maiuta et al (2017) used parallel ribosomal gene tag sequencing to profile microbes from industry-based liquid in water-miscible MWF samples.…”

“…This suggested that only detectable DNA and/or compromised cells were present, rather than active microbial cells. According to Di Maiuta et al (2017), Methanobrevibacter smithii was described as colonizer of the human gut system; thus, they probably had their origin from human sources. Methanogenic archaea are key to the successful operation of anaerobic bioreactors.…”