# The relationship between microbial population ATP and quantitative PCR bioburdens in diesel fuel microcosms

## TL;DR

This study compares ATP and qPCR methods to measure microbial bioburdens in diesel fuel microcosms, finding variable correlations depending on the sample matrix.

## Contribution

The study introduces a comparative analysis of ATP and qPCR for microbial quantification in different fuel microcosm matrices.

## Key findings

- Correlation between ATP and qPCR bioburdens varied by matrix, ranging from negligible to strong.
- qPCR bioburden ratings were typically higher than ATP ratings across different sample categories.
- Percentage agreement between ATP and qPCR ranged from 11% to 89% depending on the matrix.

## Abstract

Historically, fuel microbiology studies have relied on culture data. Potentially relevant but unculturable bacteria were not detected. Although ATP can quantify total microbial bioburdens in fuels, it cannot differentiate among the taxa present. Quantitative PCR (qPCR) testing promises to fill this gap by quantifying targeted amplicon sequences thereby detecting both culturable and non-culturable taxa and quantifying specifically targeted taxa. In this study, fluid samples drawn from the fuel, interface and water phases of fuel over water microcosms were tested for cellular ATP concentration ([cATP]) and qPCR bioburdens. Additionally, surface swab samples from steel corrosion coupon surfaces exposed to each of these three phases were collected and tested for total ATP concentration ([tATP]) and qPCR bioburdens. Statistical relationships between ATP and qPCR bioburdens were examined. Correlation coefficients between the two variables were matrix dependent and ranged from negligible (|r|=0.2) to strong (|r|=0.7). When results were categorized into negligible, moderate and heavy bioburdens, parameter agreement was again matrix dependent. Percentage agreement between [ATP] and qPCR gene copies ranged from 11 % to 89 % – with qPCR-bioburden ratings typically being greater than ATP-bioburden ratings.