Improvements on colony morphology identification towards bacterial profiling

Abstract

Colony morphology may be an indicator of phenotypic variation, this being an important adaptive process adopted by bacteria to overcome environmental stressors. Furthermore, alterations in colony traits may reflect increased virulence and antimicrobial resistance. Despite the potential relevance of using colony morphological traits, the influence of experimental conditions on colony morphogenesis has been scarcely studied in detail. This study aims to clearly and systematically demonstrate the impact of some variables, such as colony growth time, plate colony density, culture medium, planktonic or biofilm mode of growth and strain genetic background, on bacterial colony morphology features using two Pseudomonas aeruginosa strains. Results, based on 5-replicate experiments, demonstrated that all variables influenced colony morphogenesis and 18 different morphotypes were identified, showing different sizes, forms, colours, textures and margins. Colony growth time and composition of the medium were the variables that caused the highest impact on colony differentiation both derived from planktonic and biofilm cultures. Colony morphology characterization before 45 h of incubation was considered inadequate and TSA, a non-selective medium, provided more colony diversity in contrast to P. aeruginosa selective media. In conclusion, data obtained emphasized the need to perform comparisons between colony morphologies in equivalent experimental conditions to avoid misinterpretation of microbial diagnostics and biomedical studies. Since colony morphotyping showed to be a reliable method to evaluate phenotypic switching and also to infer about bacterial diversity in biofilms, these unambiguous comparisons between morphotypes may offer a quite valuable input to clinical diagnosis, aiding the decision-making towards the selection of the most suitable antibiotic and supportive treatments.

Evaluation of antimicrobial activity from native wine yeast against food industry pathogenic microorganisms

“…Antagonism of yeast with microorganisms mainly occurs due to competition for nutrients, pH changes, and the production of organic acids (Buyuksirit and Kuleasan, 2014;Sigler & Höfer, 1991), in addition to mechanisms based on the secretion of antimicrobial compounds such as killer toxins. All these methods are an important area of research into natural biocontrollers of industrial interest (Hatoum et al, 2012).…”

“…It has been reported that wild strains exhibit greater antimicrobial resistance than strains of the collection because the former are exposed to various environmental factors that force them to create efficient mechanisms to adapt to the environment, making them more resistant than a strain from the collection (Davidson & Harrison, 2002;Sousa, Machado, Nicolau, & Pereira, 2013). For that reason, wild strains were not used for subsequent experiments.…”

“…Various mechanisms have been proposed for this antagonistic activity, including parasitism of the pathogen, the induction of host resistance, and the formation of biofilms. More recently, the participation of reactive oxygen species as a defensive response (Liu, Sui, Wisniewski, Droby, & Liu, 2013), competition for nutrients and space, changes in pH, and the production of organic acids (Buyuksirit and Kuleasan, 2014;Sigler & Höfer, 1991) have been studied. Other studies have focused on the secretion of antimicrobial compounds such as killer toxins, which currently constitute an area of research into natural biocontrollers of industrial interest (Hatoum, Labrie, & Fliss, 2012).…”

Generalized spectral light scatter models of diverse bacterial colony morphologies

“…The colony model was assumed to be a spatial modulator that affects the amplitude and phase of the incident light wave . The shape of a bacterial colony is described in terms of form, elevation, margin, texture, size and color . In this paper, only the effect of the form and elevation were studied, neglecting the others.…”

Evaluation of the sterilization effect of a new mercury-free UVC light source

“…C. albicans (ATCC10231), S. aureus (ATCC25923), P. aeruginosa (ATCC9027), and E. coli (ATCC25922) obtained from American Type Culture Collection, were cultured at 37°C in tryptic soy broth (pH 7.2, BD Diagnosis Systems, Sparks, MD) [13][14][15] . All the bacteria and yeast kept on a rotary shaker at 220 rpm were cultivated for 8 h. The concentration of cells was 10 9 CFU/ml as assessed by 600 nm absorption.…”