Assessing ureolytic bacteria with calcifying abilities isolated from limestone caves for biocalcification

Abstract

Biocalcification through the use of ureolytic bacteria and biochemical activities has evolved in recent decades into a fervent resourceful effective technology suitable for soil stabilization, crack repair and bioremediation. Extensive studies have been carried out on numerous ureolytic bacterial species isolated from soils and sewage samples. However, very limited attention has been given to limestone caves with natural calcite formations as a possible source for isolation of ureolytic bacteria. In this study, bacterial isolates were recovered from limestone cave samples to determine their suitability for biocalcification. Twenty‐seven morphologically distinct bacterial isolates were identified by partial 16S rRNA gene sequencing and their various genetic diversity was characterized according to their phylogenetic affiliations. Based on the molecular identification, Sporosarcina was the most abundant genus among all the ureolytic isolates, while the rest belonged to Pseudogracilibacillus and Bacillus genera. Analytical analysis on urease measurement showed that urease activities for the isolates ranged from 1·130 to 21·513 mol urea hydrolysed per minute, with isolate NB33 achieving the highest value and TSB4 achieving the lowest value. The estimated CaCO3 precipitates for the isolates ranged from 4·04 to 17·26 mg ml−1, with isolate NB30 achieving the highest value and TSB20 achieving the lowest value. The findings in this study demonstrated that the ureolytic bacteria from limestone caves are promising bio‐calcifying agents. Significance and Impact of the Study Ureolytic bacteria continues to play an important role as microbial tools used in geotechnical engineering for soil biocalcification. Microbial strains with the ability to produce urease enzyme and induce calcium carbonate mineral are often isolated from soil, water and sludge samples. However, screening for these essential microbes from extreme regions such as caves are rarely investigated. In this study, native bacteria which were isolated from limestone cave samples are identified and characterized. The findings suggested that these ureolytic bacterial isolates have the potential to serve as suitable alternative microbial agents for soil strengthening and stabilization.

Calcium Carbonate Precipitation by Urease and Carbonic Anhydrase Positive Bacteria

“…Similar to our results many bacterial strains including Bacillus and Pseudomonas with high enzyme activities showed high CaCO3 precipitation [33]. Omoregie et al [22] reported that urease activities for the bacteria isolated from limestone caves had higher urease activity. In addition, Sun et al [21] emphasized that the urease activity of B. megaterium was lower than that of S. pasteurii at high temperatures such as 25 °C and 30 °C.…”

“…Also these results were parallel to our results. On the other hand, there are no correlation between urease activity and bio-calcification [22]. Besides these, Bacillus aerius U2 achieved maximum calcium carbonate precipitate at the end of a longer incubation (14 days) compared to S. pasteurii ATCC 6453 (7 days).…”

Pollution Intensity of Hazardous Metals, Microbiome and Potential Bacterial-Based Toxic Metal Sequestration of Coal Mine Drainage

“…As the growth remains stationary and pH further increased to >8.2, urease activities were at least 253 U ml -1 in all the cultures. Urease activities observed in this report were assumedly the rst at acidic pH, which compared favourably with values recorded at alkaline pH in previous studies [7,16,41,43]. Moreover, pH of the culture system kept increasing, alleviating the acidity condition that initially prevailed in the AMD system.…”

“…The bacteria (particularly Acinetobacter pittii, Pseudomonas citronellolis, and Bacillus cereus) have been involved in degradation of indole, a heterocyclic aromatic compound found in coal, via attack on either/or both the carbocyclic and N-heterocyclic rings [37]. Studies involving Acinetobacter [38], Enterobacteriaceae [39], Pseudomonas [40], Sporosarcina [7,41], Bacillus [41], and Exiguobacterium [38] OTUs for sequestration of toxic metals/metalloids in environmental media have been reported. Bioaccumulations of Cd, Co, and Zn were reported for Sporosarcina sp.…”

Human activities’ impacts on cave microbial diversity: perspectives for cave microbial diversity conservation

“…These microorganisms were determined to be used in the construction of bio-concretes, crack healing in concretes, and soil bioremediation. In addition, diverse enzyme activities revealed in cave isolates can serve industrial uses with low energy spending [11,22,24,25]. Wastes bioremediation potentials were detected also in cave isolates [5,25].…”