Sporulating behavior of Bacillus licheniformis strains influences their population dynamics during raw milk holding

Abstract

To understand the role of strain variability, population dynamics of 2 strains of Bacillus licheniformis, ATCC 6634 and ATCC 14580, were modeled as a function of temperature (4.0-12.0°C) and duration (0-72 h) using regression analysis. Based on the initial spiking of vegetative cells (approximately 4.0 log cfu/mL) and spores (approximately 2.0 log cfu/mL), regression equations, elucidating B. licheniformis growth behavior during raw milk holding at low temperature, were obtained. Contour plots were developed to determine the time-temperature combinations, keeping the population changes to less than 1.0 log. In vegetative cell spiking study of B. licheniformis ATCC 6634 (S1), cell population changes remained below 1.0 log up to 72 h at 8°C. For B. licheniformis ATCC 14580 (S2), 1.0 log shift was not observed only after 80 h at 8°C, indicating higher multiplication potential of S1 as compared with S2. As S2 was a readily sporulating strain, the vegetative spiking study showed spore formation at different storage temperatures. Evidence of some parallel germination was observed for this strain at 8°C or higher, when raw milk samples were spiked with spores. The experimental values obtained for sporeformers and spore counts were validated with contour plot-generated values. Overall, for raw milk samples predominated by the low sporulating strain, the contour plots suggested holding at 8°C or below for up to 72 h. In the case of the readily sporulating strain (S2), raw milk could be held at 8°C for 80 h, where little or no sporulation is observed. Sporulation behavior, germination and multiplication ability, strain variability, and temperature and duration of holding raw milk influenced the population dynamics of Bacillus species. However, in the presence of equivalent numbers of both types of sporulating strains in raw milk, despite strain variability, holding milk at 8°C for not more than 72 h would keep any cell population changes below 1.0 log. In addition, under these storage conditions, the population would remain as vegetative cells that are likely to be inactivated by pasteurization. The contour plots, so generated, would help predict the population shifts and define optimum holding conditions for raw milk before further processing.

Prevalence and Antibiotic Resistance of Bacillus sp. Isolated from Raw Milk

“…In addition, it is important to remember the correct storage conditions for raw milk before further processing. Awasti et al [53] conducted a study on strains of Bacillus licheniformis, which was also present in our samples. Their results indicate that factors such as temperature and storage time of raw milk affected changes in the growth of Bacillus sp.…”

Pathogens associated with houseflies from different areas within a New York State dairy

“…(3) Some of the bacterial species found in the present study have been previously classified as milk-spoiling organisms (Scheldeman et al, 2004;Scatamburlo et al, 2015;Awasti et al, 2019), and these included B. licheniformis and Lysinibacillus sphaericus, which were found in flies collected in the milking parlor and the sick pen, Pseudomonas aeruginosa found in the calf hutch and the sick pen, and Paenibacillus lactis isolated from 1 fly of the milking parlor. Before this study, none of these 3 organisms have been isolated from houseflies collected in dairies.…”

Effects of microsized rice straw on soil clay dispersibility

“…It has been demonstrated that B. amyloliquefaciens efficiently degrades straw lignin by secreting important enzymes, such as lignin peroxidase (LiP), manganese peroxidase (MnP) and laccase (Lac), that are involved in the destruction and degradation of the lignin structure (Mei et al, 2020). B. amyloliquefaciens spores can also be negative charge carriers (due to their surface functional groups and nonspecific assortment of ions and molecules on the cell surface) (Pesce et al, 2014; Wilson et al, 2001), and their population grows quickly (mean generation time of Bacillus species of ~30 min at ~30°C) (Awasti et al, 2019). Therefore, in the context of this study, the addition of B. amyloliquefaciens could have resulted in chemical and morphological changes (Figures 1 and 7) that increased the number of charged particles (Figure 5b); hence, the straw powder and soil clays were more effectively favoured to disperse (Figure 6b).…”