Broken Cell Walls Research Articles

An in vitro and in vivo approach to characterize digesta from pigs fed different forms of pea flour.

In vitro models of digestion are useful tools to explore the behavior of dietary fiber sources in gastrointestinal conditions. To evaluate the validity of our digestion model, digesta obtained in vivo and in vitro were characterized and the impact of cell wall integrity on protein bioaccessibility and digestibility evaluated. Six cannulated barrows [Pietrain × (Large White × Landrace)] were included in a 2 × 2 Latin square design where they were fed two diets identical in chemical composition but differing in nutrient bioaccessibility. Pea was given either as flour (R1, most proteins encapsulated by intact cell walls) or reconstituted flour (R2, mixture of proteins and purified, broken cell walls). Digesta were collected at the duodenal and ileal cannulas at regular interval and after slaughtering, following ingestion of either R1 or R2. The two diets were also digested in vitro using a static gastrointestinal model. The original pea ingredients as well as the digesta collected in vivo and in vitro were characterized (i.e., particle size measurement, microscopy observations and gel electrophoresis) and then compared with each other. The degradation of the pea ingredients differed greatly between the two forms of flour, where particles filled with nutrients were recovered at the latest stage of R1 intestinal digestion as observed with the particle size distribution and the microscopy images. These results were consistent with the in vivo and in vitro digestibility analysis that showed lower protein hydrolysis for R1 than that for R2 (about 19% difference in protein digestion regardless of the method). Overall, great similarities were found between the digesta collected in vivo and in vitro, especially regarding the particle size measurements. To summarize, a substantial proportion of the proteins contained in R1 was retained within the pea cells following gastrointestinal digestion. These encapsulated proteins reduced the amount of amino acids and small peptides available for absorption. This mechanism will have consequences on postprandial metabolism of amino acids and bacterial population based on the delivery form of the dietary fiber.

An In Vitro Analysis and In Vivo Trial Demonstrating the Improved Iron Bioavailability of White Beans (Phaseolus vulgaris L.) After Processing Into Pasta

Abstract Objectives The cotyledon cell wall of the common bean can be a factor in Fe bioavailability. This study evaluated the iron bioavailability of two bean varieties (white or black) either boiled (intact cell walls) or extruded into pasta formulated from heat treated bean flour as the major ingredient (100% bean flour; broken cell walls). Methods In vitro Fe bioavailability was determined via the Caco-2 Cell Bioassay. In vivo Fe bioavailability was measured by the capacity of a bean-based or bean pasta-based diet to generate and maintain total body hemoglobin iron (Hb-Fe) during a 6 week poultry feeding trial. Results The iron and phytate concentrations of the bean-based and bean pasta-based diets consisting of tomato paste, carrot, cabbage, milk, potato and corn oil were not significantly different. The Caco-2 cell bioassay predicted that the white bean pasta diet would have the highest Fe bioavailability, closely followed by the white bean diet. The bioassay predicted the black bean diet and the black bean pasta diet would have significantly lower Fe bioavailability. For the in vivo studies, animals fed the white bean pasta diet (broken cell walls) had significantly (p ≤ 0.05) higher hemoglobin, Hb-Fe and hemoglobin maintenance efficiencies than animals fed a white bean, black bean or black bean pasta-based diet. Although cotyledon cells were broken, the iron bioavailability of the black bean pasta was not improved after processing into pasta. The low iron bioavailability of black beans was associated with their high concentrations of seed coat procyanidin, cinnamtannin and anthocyanidin compounds that have a negative impact on the absorption of iron. Conclusions This study shows that white colored dry bean possesses a combination of traits that result in improved iron bioavailability after processing into pasta. The enhanced Fe bioavailability from the white bean pasta is likely due to the breakage of the cotyledon cell wall during processing, thus allowing enhanced bioaccessibility of the intracellular Fe. In the black bean pasta diet, this enhancement was not observed due to the presence of the seed coat polyphenols which interacted with the released intracellular Fe and prevented Fe absorption. Funding Sources Funded by the United States Department of Agriculture, Agricultural Research Service.

The use of kidney bean flour with intact cell walls reduces the formation of acrylamide in biscuits

Acrylamide (AA) is formed by Maillard Reaction (MR), during high-temperature and low moisture processes in several food categories, including bakery products. AA is classified as a toxic and carcinogenic compound and therefore, mitigation strategies are necessary to control its concentration in foods. Selecting ingredients with a reduced amount of asparagine, the main AA precursor, is the most effective method of reducing the AA formation in bakery products.In the present study, the hypothesis that cotyledon cell walls integrity could prevent the formation of AA by modulating the dehydration rate and reducing the availability of asparagine during the MR development during baking was investigated. Legumes have strong cotyledon cell walls that can be preserved during flour production: in this study two kidney bean flours with intact and broken cell walls were used. The integrity of the cotyledon cell walls was assessed by scanning electron microscopy while AA, its precursors, moisture and water activity were measured in bean flours, raw doughs and baked biscuits. The biscuits were also characterised for the main baking parameters such as weight loss, pH, colour and texture.The results showed that biscuits formulated with bean flour with intact cell walls had a 15% less amount of AA than those made with the bean with damaged cell walls at the end of the cooking time. Furthermore, the use of the two different bean flours led to different quality characteristics of the biscuits in terms of hue angle and browning index, as colour parameters, and hardness, which is related to the texture properties. These differences were attributed to the different development of the MR and in the structure of the biscuit during baking. The use of intact plant tissue legume flours in alterative biscuits formulations is a feasible and low-cost approach that can contribute to the AA mitigation strategy.

Combinations of Peptide-Protein Extracts from Native Probiotics Suppress the Growth of Multidrug-Resistant Staphylococcus aureus and Citrobacter freundii via Membrane Perturbation and Ultrastructural Changes.

The occurrence of multidrug-resistant pathogens in the food chain causes health problems in humans, thus, research for novel antimicrobials to combat their growth is of interest. This study evaluates the antimicrobial potential of several combinations of peptide-protein extracts (PCs) consisting of peptide extracts from three native probiotic strains, Lactiplantibacillus plantarum UTNGt2, Lactococcus lactis UTNGt28, and L. plantarum UTNGt21A, alone or in combination with EDTA (ethylenediaminetetraacetic acid) against multidrug-resistant Staphylococcus aureus ATCC1026 and Citrobacter freundii UTNB3Sm1. Based on the antimicrobial assay, among the 19 tested PCs, two (PC11 and PC17) produced a greater zone of inhibition against both pathogens in vitro. Time-killing assays indicated the rapid death of S. aureus after exposure to PC11 and PC17, while C. freundii was rapidly inhibited by PC11 and PC1 (UTNGt2 only), suggesting that the inhibitory action is pathogen and dose-dependent of a particular molecule present in the extract. A marginal inhibitory effect was observed when the peptides were combined with EDTA. Transmission electron microscopy (TEM) revealed the structural membrane damage of both target strains upon interaction with individual peptide extracts. Different degrees of cell deformation, condensed cytoplasm, membrane blebbing, and ghost cell formation with visibly broken cell walls were observed in S. aureus. Likewise, the separation of the cytoplasmic membrane from the outer membrane, ghost cells, along with ovoid and deformed cells with undulated cell walls were observed for C. freundii. Furthermore, scanning electronic microscopy (SEM) analysis revealed different wrinkled and deformed cells covered by debris. A leakage of aromatic molecules was detected for both pathogens, indicating that PCs disrupted the cell wall integrity, inducing cell death. Given their inhibitory action and capacity to induce damage of the cytoplasmic membrane, the selected PCs may serve to slow bacterial growth in vitro; further research is required to prove their efficiency ex vitro to battle against food poisoning and subsequent human infection.

Antibacterial effect of Blumea balsamifera DC. essential oil against Haemophilus parasuis.

Haemophilus parasuis (H. parasuis), the cause of the Glasser's disease, is a potentially pathogenic gram-negative organism that colonizes the upper respiratory tract of pigs. The extraction of Blumea balsamifera DC., as a traditional Chinese herb, has shown great bacteriostatic effect against several common bacteria. To study the antibacterial effect on H. parasuis in vitro, this study evaluated the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of Blumea balsamifera DC. essential oil (BBO) as well as morphological changes in H. parasuis treated with it. Furthermore, changes in expression of total protein and key virulence factors were also assessed. Results showed that the MIC and MBC were 0.625 and 1.25μg/mL, respectively. As the concentration of BBO increased, the growth curve inhibition became stronger. H. parasuis cells were damaged severely after treatment with BBO for 4h, demonstrating plasmolysis and enlarged vacuoles, along with broken cell walls and membranes. Total protein and virulence factor expression in H. parasuis was significantly downregulated by BBO. Taken together, these results indicated a substantial antibacterial effect of BBO on H. parasuis.

Accumulation of long-chain fatty acids from Nannochloropsis salina enhanced by breaking microalgae cell wall under alkaline digestion

Breaking cell wall is a key step for extracting intracellular components such as proteins and lipids from microalgae. This study investigated an alternative way to disrupt microalgae cell structure by controlling pH during anaerobic digestion. The undigested lipid fractions from microalgae was preserved as long chain fatty acids (LCFAs) through pH control at alkaline condition. The optimum anaerobic hydrolysis was observed under alkaline condition at pHs 10 and 11; a maximum concentration of LCFAs (1150 mg/L) was observed at pH 11.0 on the fourth day of anaerobic digestion, which mainly consisted of palmitic acid and palmitoleic acid. Under alkaline condition, no methane was produced because of the inhibition of methanogenesis. However, the efficiency of organics hydrolysis was significantly enhanced as more soluble chemical oxygen demand (SCOD) was detected at pH 10 (11,170 mg/L SCOD) and pH 11 (12,273 mg/L SCOD), which was nearly twice higher than neutral pH. Also, confocal and transmission electron microscopy images illustrated the damage of microalgae cell wall and distribution of released LCFAs. The results provide insight for developing low-cost options for harvesting lipids from algal biomass.

Structural insights reveal the effective Spirulina platensis cell wall dissociation methods for multi-output recovery

In this work, Spirulina platensis cells harvested in the exponential and equilibrium phases with intact and broken cell walls were treated through a set of alkaline or acidic conditions including alkalis and acids, with solutions of pH 0.0–14.0. The effective Spirulina platensis cell wall dissociation methods for multi-output recovery were obtained. SEM and FTIR were applied to characterize the alkaline and acid treatment details, and Spirulina platensis cell wall dissociation mechanisms, via attacks by OH− or H+, were then proposed. Overall, this study highlights the synthesized multi-output algal product in an integrated strategy with ultracellular structural insight and is valuable for understanding the specific roles of attack ions.

Clues for Cellular Structure Optimization in Aluminum Foams

This work studies the different stages of the fabrication of aluminum foams from PM precursors and aims on finding the parameters affecting the generation of defects in the cellular structure. Results show that foam's cellular anisotropy is directly related to the structural anisotropy of the initial precursor and the way it starts expanding. Homogenization heat treatment to the precursor material can then reduce foam's cellular anisotropy. On the other hand, the amount of broken cell walls depends not only on the expansion grade, but more significantly on the cooling conditions at the end of the foaming process, being this a possible key to reduce and control their generation.

Evaluation of the antimicrobial activity of 9-oxo-agerophorone against soil borne pathogens

9-Oxo-agerophorone is a cadinene sesquiterpene, isolated from the leaves of Eupatorium adenophorum. This study evaluated the antimicrobial activity of 9-oxo-agerophorone against three strains of Ralstonia solanacearum and four pathogenic fungi, with an emphasis on the growth and morphogenesis of fungi at scanning electron microscopy level. The determination of minimal inhibitory concentrations demonstrated that 9-oxo-agerophorone exhibited moderate bactericidal activity against R. solanacearum strains. However, antifungal assays showed that 9-oxo-agerophorone has strong toxicity against Fusarium oxysporum, Bipolaris sorokiniana, Fusarium proliferatum, and Alternaria tenuissima with median lethal concentrations ranging from 0.476 to 0.357 mg ml−1 after 4 days incubation on potato dextrose agar medium. The main changes observed by scanning electron microscopy after 9-oxo-agerophorone treatment were fungal cell wall shrinkage, loss of conidia, formation of short branches in F. oxysporum and F. proliferatum, collapse, broken cell walls, and increased hyphae diameter in A. tenuissima. The tested treatments were also effective in inhibiting spore germination of Fusarium species. The results indicated that 9-oxo-agerophorone is a potential candidate as a phytotherapeutic agent for soil-borne fungal diseases.

Defining New Drug Targets Through Protein-Protein Interaction: Interaction of Resuscitation Promoting Factors with SucA of TCA Cycle in M. tuberculosis H37Rv

Upon infection with Mycobacterium tuberculosis, only a small percentage causes active infection while the rest goes into latent infection. These latent bacilli can reactivate under immunocompromised conditions and cause active disease. Little is known about the mechanism by which the mycobacteria reactivate. A family of extracellular bacterial proteins, known as resuscitation promoting factors (Rpf) from Micrococcus luteus and M. tuberculosis has been shown to stimulate growth of dormant mycobacteria as well as reactivation of chronic tuberculosis in mice. Rpf is present as a single, essential gene in M. luteus and five homologues (rpfA-E) in M. tuberculosis. The ability to stimulate culturability and resuscitation appears to be related to muralytic activity of Rpf and they have been identified as peptidoglycan glycosidases. Rpf B has earlier been shown to interact and synergize with Rpf-interacting protein A (RipA), an endopeptidase to cleave bonds in bacterial peptidoglycan suggesting distinct role of Rpf B in cell wall hydrolysis. In order to further understand the role of other Rpfs in resuscitation of dormant mycobacteria, we used an E. coli two hybrid system to identify SucA of TCA cycle as an interacting partner of Rpf from M. tuberculosis (Rpf A, C and D) and M. luteus (RpfM). The in vivo protein-protein interaction was confirmed by M-PFC system in mycobacterial host, in vitro by FRET analysis. An enhanced expression of SucA and Rpf genes was observed during resuscitation phase. We hypothesize that during transition from nonculturable to resuscitation phase mycobacteria cleaves its hard breaking cell wall by endopeptidase RipA interacting with Rpf B and increases its metabolic energy generation by evoking TCA cycle, interacting with Rpf A, C and D and could serve as prospective target along with Rpfs and RipA for development of new anti-tuberculosis drugs preventing reactivation of dormant bacilli.

Oxidative injury and antioxidant enzymes regulation in arsenic-exposed seedlings of four Brassica napus L. cultivars.

Environmental contamination due to arsenic (As) has become a major risk throughout the world; this affects plant growth and productivity. Its accumulation in food chain may pose a severe threat to organisms. The present study was carried out to observe the toxic effects of As (0, 50, 100, and 200 μM) on physiological and biochemical changes in four Brassica napus cultivars (ZS 758, Zheda 619, ZY 50, and Zheda 622). Results showed that As toxicity provoked a significant inhibition in growth parameters of B. napus cultivars and this reduction was more obvious in cultivar Zheda 622. The highest concentration of MDA, H2O2, and O2 (-) contents in both leaf and root tissues were observed at 200 μM As level, and a gradual decrease was observed at lower concentrations. Increasing As concentration gradually decreased chlorophyll and carotenoids contents. Activity of antioxidant enzymes such as SOD, CAT, APX, GR, and GSH was positively correlated with As treatments in all cultivars. The microscopic study of leaves and roots at 200 μM As level showed the disorganization in cell organelles. Disturbance in the morphology of chloroplast, broken cell wall, increase in size, and number of starch grains and immature nucleus were found in leaf ultrastructures under higher concentration of As. Moreover, damaged nucleus, diffused cell wall, enlarged vacuoles, and a number of mitochondria were observed in root tip cells at 200 μM As level. These results suggest that B. napus cultivars have efficient mechanism to tolerate As toxicity, as evidenced by an increased level of antioxidant enzymes.

Chromium-induced physio-chemical and ultrastructural changes in four cultivars of Brassica napus L.

In nature, plants are continuously exposed to several biotic and abiotic stresses. Among these stresses, chromium (Cr) stress is one of the most adverse factors that affects the plant growth, and productivity, and imposes a severe threat for sustainable crop production. In the present study, toxic effects of Cr were studied in hydroponically grown seedlings of four different cultivars of Brassica napus L. viz. ZS 758, Zheda 619, ZY 50 and Zheda 622. The study revealed that elevated Cr concentrations reduced the plant growth rate and biomass as compared to respective controls in all the cultivars and this decline was more obvious in Zheda 622. It was observed that reduction of photosynthetic attributes was more pronounced in Zheda 622 as compared to other cultivars; while, cultivar ZS 758 performed better under Cr-toxicity. Results showed that Cr contents in different parts of seedlings were higher in Zheda 622 as compared to other cultivars and Cr contents were higher in roots than shoots in all the cultivars. Accumulation of reactive oxygen species (ROS) and malondialdehyde (MDA) were induced under different Cr concentrations. Results showed that some of anti-oxidant enzyme activities in leaves and roots were increased under the Cr-toxicity. The electron microscopic study showed that ultrastructural damages in leaf mesophyll and root tip cells were more prominent in Zheda 622 as compared to other cultivars under 400μM Cr stress. Under 400μM Cr concentration, changes like broken cell wall, immature nucleus, a number of mitochondria, ruptured thylakoid membranes and large size of vacuole and starch grains were observed in leaf ultrastructures. The damages in root cells were observed in the form of disruption of golgibodies and diffused cell wall under the higher concentration of Cr (400μM). On the basis of these observations, it was concluded that Zheda 622 was found to be more sensitive as followed by ZY 50, Zheda 619 and ZS 758 under Cr-toxicity.

Influence of Local Wall Variation in the Elastic Properties of Planar Cellular Solids

A numerical model based on one-dimensional cell wall behavior is used to study the influence of changes in the cell wall properties on the global stiffness parameters of two-dimensional open-celled honeycombs. Following validation of results for intact microstructures, cases are considered, including regular and irregular cellular structures, structures with missing/broken cell walls, and structures with cell walls of non-uniform thickness. The influence of each of these flaws or changes in microstructure is quantified, with broken cell walls dominating changes in bulk behavior and varying cell wall thickness resulting in changes to bulk properties that can be considered negligible.

Effect of particle size and temperature on rheological, thermal, and structural properties of pumpkin flour dispersion

Controlling the rheological properties of dispersion has been of great interest in the food processing industry. Effects of particle size and temperature on oscillatory rheology of pumpkin flour dispersion were studied. Fresh pumpkin was freeze-dried, grinded and sieved through selected screens to obtain desired particle size fractions (74–841μm). Most of the particles are spherical in shape. The glass transition temperature (Tg) and the melting temperature (Tm) of starch–lipid complex varied with particle size which is believed to be due to compositional variations. Rheological measurement of reconstituted particles as a function of temperature (10–90°C) and concentration (4–10% w/w) indicated a solid-like behavior (G′>G″). Sediment volume fraction (ϕ) of isolated particle dispersions indicated a gradual decrease with decrease in particle size, which directly influences the mechanical strength and visco-elasticity of the dispersion. Particle size influenced the mechanical rigidity of pumpkin dispersion markedly whereas the temperature had the least effect. An unexpected increase in G′ of finest particle containing dispersion with temperature could be associated with gelatinization of starch and flocculation of particles with broken cell walls. Microscopic observation revealed the presence of a continuous network for the finest particle dispersion, as opposed to discontinuous one for other particle sizes.

Structural alterations in plant compound treated Trichophyton tonsurans

The ultra structural changes were studied in Trichophyton tonsurans –a clinical isolate, treated with compound ({ά(2-hydroxy-2methylpropyl)-ω[2-hydroxy-3-methylbut-2-en-1-yl] polymethylene}), isolated from ethyl acetate leaf extract of Caesalpinia bonducella. Compound microscopy studies reveal; on normal SDA medium, the germ tubes grew rapidly; long and regularly branched, and their tips appeared normal. But on SDA medium containing 100, 200 and 300 μg/ml of compound, spherical hyphae or bamboo-like-joint hyphae occurred after 7 days of incubation. Hyphae developing from the abnormally swollen microconidia were spherical or ellipsoid and shorter and thicker than those developing from normal microconidia. Though all the three concentrations of compound caused morphological changes in Trichophyton tonsurans, the most prominent change seen in T. tonsurans treated with 300 μg/ml of compound was characterized by several findings: (i) irregular hyphae with broken cell wall, which was the result of longer exposure time; wavy or shrunken hyphae; (ii) extrusion of cellular materials. However in the control, the hyphae were regular and branched with normal tips.

Histological aspects of the cryopreservation of potato

Cryopreservation appears to be a suitable solution for the maintenance of potato germplasms. The protocol described in this paper can be applied for the vitrification and preservation of meristems. During histo-cytological studies it is possible to observe modifications at the cellular level and to understand the adaptive mechanism to low temperatures. Control potato meristem tissue contained a number of meristematic cells with a gradient of differentiation. After freezing there were a large number of vacuolated cells, some of which exhibited broken cell walls and plasmolysis. The thickening of the cell wall, giving them a sinuous appearance, was observed after freezing and thawing the meristems, with ruptures of the cuticle and epidermal layer.

Histological studies of damage by pod-sucking bugs (Heteroptera: Coreoidea) associated with cowpea Vigna unguiculata ssp. unguiculata in Nigeria

Histological studies were conducted on cowpea pods fed upon by the coreoid pod-sucking bugs, Anoplocnemis curvipes (Fabricius), Clavigralla tomentosicollis Stål, C. shadabi Dolling, Riptortus dentipes (Fabricius) and Mirperus jaculus (Thunberg). Various degrees of tissue and cellular disruption were apparent, especially in the brachysclereids. They were manifested in terms of plasmolysis, cell enlargement and cell wall disintegration depending on the coreoid species involved. The feeding site and its periphery had all the cells of the brachysclereids plasmolysed, with the parenchyma having broken cell walls in the case of A. curvipes. Riptortus dentipes and M. jaculus showed similar patterns of feeding activity but less extensive levels of damage. The Clavigralla spp., however, caused cell enlargement in the brachysclereids, and broken cell walls in both the brachysclereids and the parenchyma. Damage symptoms were observed in cells far away from the feeding sites of the bugs, suggesting the possibility of sucrase activity which has been reported to cause osmotic pump feeding in the Coreidae.

Molecular level damages of low power pulsed laser radiation in a marine bacterium Pseudoalteromonas carrageenovora

To study the molecular level damages in a marine bacterium, Pseudoalteromonas carrageenovora, exposed to low power pulsed laser radiation from an Nd:YAG laser. The laser damages in bacterial DNA were monitored by studying the formation of apurinic/apyrimidinic (AP) sites. Molecular probe kits were used for this purpose. Occurrence of lesions in the cell walls was monitored under a transmission electron microscope (TEM). The results showed that laser radiation significantly increased the number of AP sites in the bacterial DNA. This increase corresponded to the laser fluence (J cm(-2)) and to the duration of laser irradiation. TEM observation showed the occurrence of lesions in bacterial cell walls upon laser irradiation. It is concluded that bacteria exposed to laser irradiation suffers DNA damages and resulted in broken cell walls. These events led to bacterial mortality. These are in addition to the mechanisms reported earlier such as the photochemical reactions occurring inside the cells upon exposure to low power laser. These results help us to understand the mechanisms of bacterial mortality on exposure to low power pulsed laser irradiation and are useful in formulating a laser treatment strategy to kill bacteria.

Effect of osmotic dewatering on apple tissue structure

Apple cubes were subjected to osmotic dehydration in 61.5% sucrose and changes in tissue structure were examined in light microscope. Fixed and embedded in raisin 3 μm thick slices were analysed and indices characterising apple tissue structure were calculated with computer image analysis. It was found that osmotic dehydration affects size and shape of cells, and in consequence changes shape and dimension of intercellular spaces. No broken cell walls were found in osmosed tissue. Osmotic treatment increased the share of small cells in tissue and moved shape factor toward smaller values. There was a difference in response of cells to osmotic stress dependent on the cell location. Cells, which are in contact with intercellular spaces reacted to osmotic stress in different way than those surrounded by other cells. Shrinkage of cells and deformation of cell walls caused increase of circumference of intercellular spaces. The increase was more than 30% until 120 min of osmosis. Moreover, intercellular spaces became more irregular than those did in raw apple. Further osmotic treatment caused substantial increase of small intercellular spaces, which was probably due to detachment of some cells and splitting of middle lamella. This observation suggested that prolonged osmotic dehydration could disintegrate apple tissue and destroy its continuity.

ISOLATION AND CHARACTERIZATION OF A CELL WALL‐DEFECTIVE MUTANT OF CHLAMYDOMONAS MONOICA (CHLOROPHYTA)1

Cell wall–defective strains of Chlamydomonas have played an important role in the development of transformation protocols for introducing exogenous DNA (foreign genes or cloned Chlamydomonas genes) into C. reinhardtii. To promote the development of similar protocols for transformation of the distantly related homothallic species, C. monoica, we used UV mutagenesis to obtain a mutant strain with a defective cell wall. The mutant, cw‐1, was first identified on the basis of irregular colony shape and was subsequently shown to have reduced plating efficiency and increased sensitivity to lysis by a non‐ionic detergent as compared with wild‐type cells. Tetrad analysis of crosses involving the cw‐1 mutant confirmed 2:2 segregation of the cw:cw+ phenotypes, indicating that the wall defect resulted from mutation of a single nuclear gene. The phenotype showed incomplete penetrance and variable expressivity. Although some cells had apparently normal cell walls as viewed by TEM, many cells of the cw‐1 strain had broken cell walls and others were protoplasts completely devoid of a cell wall. Several cw‐1 isolates obtained from crosses involving the original mutant strain showed a marked enhancement of the mutant phenotype and may prove especially useful for future work involving somatic cell fusions or development of transformation protocols.