Category: Ola Olapade (Faculty Co-author)

Lauren Rasmussen, ’17

Olapade, O. A., & Rasmussen, L. (2019). Effects of iron and copper treatments on the bacterioplankton assemblages from surface waters along the north branch of the Kalamazoo River, Michigan, USA. Journal of Basic Microbiology, 59(4), 385-391.

Abstract: The effects of varying concentrations (ranging from 0 to 10 μM) of two different metals that is, iron (Fe) and copper (Cu) on indigenous bacterial populations and their hydrolytic enzyme activities within the bacterioplankton assemblages from the surface waters of the Kalamazoo River were examined under controlled microcosm conditions. The two metals were added to water samples collected from the Kalamazoo River and examined for bacterial abundance and leucine aminopeptidase activities at various time intervals over a 48 h incubation period in the dark. Results revealed no concentration effects on the bacterial populations in the presence of both Fe and Cu, although the bacterial numbers varied significantly over time in both microcosms. Conversely, leucine aminopeptidase activities based on post-hoc tests using Bonferroni correction revealed significant differences to increasing concentrations of both metals over the study period. These results further validate previous knowledge regarding the importance of various metal ions in regulating bacterial community structures and also suggest that aminopeptidase have the potential of effectively functioning using diverse trace and heavy metals as extracellular peptidase cofactors in aquatic systems.

Lauren Rasmussen, ’17

Rasmussen, L., & Olapade, O. A. (2016). Influence of zinc on bacterial populations and their proteolytic enzyme activities in freshwater environments: a cross-site comparison. Canadian Journal of Microbiology, 1-9.

Abstract: Temporal responses of indigenous bacterial populations and proteolytic enzyme (i.e., aminopeptidase) activities in the bacterioplankton assemblages from 3 separate freshwater environments were examined after exposure to various zinc (Zn) concentrations under controlled microcosm conditions. Zn concentrations (ranging from 0 to 10 μmol/L) were added to water samples collected from the Kalamazoo River, Rice Creek, and Huron River and examined for bacterial abundance and aminopeptidase activities at various time intervals over a 48 h incubation period in the dark. The results showed that the Zn concentrations did not significantly influence total bacterial counts directly; however, aminopeptidase activities varied significantly to increasing zinc treatments over time. Also, analysis of variance and linear regression analyses revealed significant positive relationships between bacterial numbers and their hydrolytic enzyme activities, suggesting that both probably co-vary with increasing Zn concentrations in aquatic systems. The results from this study serve as additional evidence of the ecological role of Zn as an extracellular peptidase cofactor on the dynamics of bacterial assemblages in aquatic environments.

Adam Ronk, ’13

Olapade, O. A., & Ronk, A. J. (2014). Isolation, Characterization and Community Diversity of Indigenous Putative Toluene-Degrading Bacterial Populations with Catechol-2,3-Dioxygenase Genes in Contaminated Soils. Microbial Ecology, 1-7.

Abstract: Indigenous bacterial assemblages with putative hydrocarbon-degrading capabilities were isolated, characterized and screened for the presence of the catechol-2,3-dioxygenase (C23O) gene after exposure to toluene in two different (i.e., pristine and conditioned) soil communities. The indigenous bacterial populations were exposed to the hydrocarbon substrate by the addition of toluene concentrations, ranging from 0.5 % to 10 % V/W in 10 g of each soil and incubated at 30 °C for upwards of 12 days. In total, 25 isolates (11 in pristine soil and 14 in conditioned soil) were phenotypically characterized according to standard microbiological methods and also screened for the 238-bp C23O gene fragment. Additionally, 16S rRNA analysis of the isolates identified some of them as belonging to the genera Bacillus, Exiguobacterium, Enterobacter, Pseudomonas and Stenotrophomonas. Furthermore, the two clone libraries that were constructed from these toluene-contaminated soils also revealed somewhat disparate phylotypes (i.e., 70 % Actinobacteria and Firmicutes to 30 % Proteobacteria in conditioned soil, whereas in pristine soil: 66 % Actinobacteria and Firmicutes; 21 % Proteobacteria and 13 % Bacteroidetes). The differences observed in bacterial phylotypes between these two soil communities may probably be associated with previous exposure to hydrocarbon sources by indigenous populations in the conditioned soil as compared to the pristine soil.

Kayleigh Pung, ’11

Olapade, O., & Pung, K. (2012). Plant-associated bacterial populations on native and invasive plant species: comparisons between 2 freshwater environments. Canadian Journal of Microbiology, 58(6), 767-775.

Abstract: Plant–microbial interactions have been well studied because of the ecological importance of such relationships in aquatic systems. However, general knowledge regarding the composition of these biofilm communities is still evolving, partly as a result of several confounding factors that are attributable to plant host properties and to hydrodynamic conditions in aquatic environments. In this study, the occurrences of various bacterial phylogenetic taxa on 2 native plants, i.e., mayapple (Podophyllum peltatum L.) and cow parsnip (Heracleum maximum Bartram), and on an invasive species, i.e., garlic mustard (Alliaria petiolata (M. Bieb.) Cavara & Grande), were quantitatively examined using nucleic acid staining and fluorescence in situ hybridization. The plants were incubated in triplicates for about a week within the Kalamazoo River and Pierce Cedar Creek as well as in microcosms. The bacterial groups targeted for enumeration are known to globally occur in relatively high abundance and are also ubiquitously distributed in freshwater environments. Fluorescence in situ hybridization analyses of the bacterioplankton assemblages revealed that the majority of bacterial cells that hybridized with the different probes were similar between the 2 sites. In contrast, the plant-associated populations while similar on the 3 plants incubated in Kalamazoo River, their representations were highest on the 2 native plants relative to the invasive species in Pierce Cedar Creek. Overall, our results further suggested that epiphytic bacterial assemblages are probably under the influences of and probably subsequently respond to multiple variables and conditions in aquatic milieus.

Kayleigh Pung, 11, Erin Goldman, ’11

Olapade, O. A., Pung, K., Goldman, E., & Lyons-Sobaski, S. (2011). Occurrence and diversity of epiphytic bacterial communities on two native plant species in a Michigan Creek. Journal of Freshwater Ecology, 26(2), 267 – 276.

Abstract: We examined the occurrence and diversity of bacteria of different phylogenetic groups in epiphytic assemblages on two native Michigan plant species mayapple (Podophyllum peltatum) and cow parsnip (Heracleum maximum) when the plant leaves were submerged in fresh water. Fresh leaves were incubated in triplicate for about a week within a creek in Hasting, Michigan, and in laboratory microcosm to develop mature epiphytic assemblages. We enumerated bacteria in these assemblages by nucleic acid staining (i.e., total direct counts using 4′,6-diamidino-2-phenyllindole) and fluorescent in situ hybridization (FISH), while community diversity was determined based on 16S rRNA gene sequencing. FISH indicated the dominance of members of the γProteobacterial subclass (20%) on both plant species, while the 16S rRNA gene analysis revealed the predominance of the βProteobacteria (51%) on mayapple and the Fermicutes (26%) on cow parsnip, with the Bacteroidetes present equally within the epiphytic assemblages on both plants.

Elizabeth Weage, ’08

Olapade, O. A., & Weage, E. A. (2010). Comparison of Fecal Indicator Bacterial Populations in Surface Waters of the Kalamazoo River, USA. Microbes and Environments, 25(1).

Abstract: Surface waters along the Kalamazoo River, USA, were examined for occurrence and population trends of fecal indicator bacteria (FIB) with culture-based and culture-independent methods. The two methods recorded discrepancies in FIB counts, with the culture-independent method revealing more consistent numbers between the river sites. FIB cells that hybridized with the ECO1482 probe were highest in the downstream site, while the upstream site recorded higher ENF343 hybridized cells. Spatial and temporal differences in FIB populations were probably attributable to contrasting fecal pollution influences, vegetation type, varying environmental conditions as well as several in-stream factors between the two river sites.

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