often allows for detailed observations of development. the cells can be harvested at any stage of development and grown quickly. while cultivating d. discoideum in a laboratory, it is important to take into account its behavioral responses. for example, it has an affinity toward light, higher temperatures, high humidity, low ionic concentrations, and the acidic side of the ph gradient. experiments are often done to see how manipulations of these parameters hinder, stop, or accelerate development. variations of these parameters can alter the rate and viability of culture growth. also, the fruiting bodies, being that this is the tallest stage of development, are very responsive to air currents and physical stimuli. it is unknown if there is a stimulus involved with spore release. protein expression studies detailed analysis of protein expression in dictyostelium has been hampered by large shifts in the protein expression profile between different developmental stages and a general lack of commercially available antibodies for dictyostelium antigens. in 2013, a group at the beatson west of scotland cancer centre reported an antibody-free protein visualization standard for immunoblotting based on detection of mccc1 using streptavidin conjugates. legionnaire's disease the bacterial genus legionella includes the species that causes legionnaire's disease in humans. d. discoideum is also a host for legionella and is a suitable model for studying the infection process. specifically, d. discoideum shares with mammalian host cells a similar cytoskeleton and cellular processes relevant to legionella infection, including phagocytosis, membrane trafficking, endocytosis, vesicle sorting, and chemotaxis. "farming" a 2011 report in nature published findings that demonstrated a "primitive farming behaviour" in d. discoideum colonies. described as a "symbiosis" between d. discoideum and bacterial prey, about one-third of wild-collected d. discoideum colonies engaged in the "husbandry" of the bacteria when the bacteria were included within the slime mold fruiting bodies. the incorporation of the bacteria into the fruiting bodies allows the "seeding" of the food source at the location of the spore dispersal, which is particularly valuable if the new location is low in food resources. colonies produced from the "farming" spores typically also show the same behavior when sporulating. this incorporation has a cost associated with it: those colonies that do not consume all of the prey bacteria produce smaller spores that cannot disperse as widely. in addition, much less benefit exists for bacteria-containing spores that land in a food-rich region. this balance of the costs and benefits of the behavior may contribute to the fact that a minority of d. discoideum colonies engage in this practice. d. discoideum is known for eating gram-positive, as well as gram-negative bacteria, but some of the phagocytized bacteria, including some human pathogens, are able to live in the amoebae and exit without killing the cell. when they enter the cell, where they reside, and when they leave the cell are not known. the research is not yet conclusive but it is possible to draw a general lifecycle of d. discoideum adapted for farmer clones to better understand this symbiotic process.lifecycle of farmer d. discoideum in the picture, one can see the different stages. first, in the starvation stage, bacteria are enclosed within d. discoideum, after entry into amoebae, in a phagosome the fusion with lysosomes is blocked and these unmatured phagosomes are surrounded by host cell organelles such as mitochondria, vesicles, and a multilayer membrane derived from the rough endoplasmic reticulum (rer) of amoebae. the role of the rer in the intracellular infection is not known, but the rer is not required as a source of proteins for the bacteria. the bacteria reside within these phagosomes during the aggregation and the multicellular development stages. the amoebae preserve their individuality and each amoeba has its own bacterium. during the culmination stage, when the spores are produced, the bacteria pass from the cell to the sorus with the help of a cytoskeletal structure that prevents host cell destruction. some results suggest the bacteria exploit the exocytosis without killing the cell. free-living amoebae seem to play a crucial role for persistence and dispersal of some pathogens in the environment. transient association with amoebae has been reported for a number of different bacteria, including legionella pneumophila, many mycobacterium species, francisella tularensis, and escherichia coli, among others. agriculture seems to play a crucial role for pathogens' survival, as they can live and replicate inside d. discoideum, making husbandry. nature’s report has made an important advance in the knowledge of amoebic behavior, and the famous spanish phrase translated as “you are more stupid than an amoeba” is losing the sense because amoebae are an excellent example of social behavior with an amazing coordination and sense of sacrifice for the benefit of the species. sentinel cells sentinel cells in dictyostelium discoideum are phagocytic cells responsible for removing toxic material from the slug stage of the social cycle. generally round in shape, these cells are present within the slug sheath where they are found to be circulating freely. the detoxification process occurs when these cells engulf toxins and pathogens within the slug through phagocytosis. then, the cells clump into groups of five to ten cells, which then attach to the inner sheath of the slug. the sheath is sloughed off as the slug migrates to a new site in search of food bacteria. sentinel cells make up approximately 1% of the total number of slug cells, and the number of sentinel cells remains constant even as they are being released. this indicates a constant regeneration of sentinel cells within the slugs as they are being removed along with toxins and pathogens. sentinel cells are present in the slug even when there are no toxins or pathogens to be removed. sentinel cells have been located in five other species of dictyostelia, which suggests that sentinel cells can be described as a general characteristic of the innate immune system in social amoebae. effects of farming status on sentinel cells the number of sentinel cells varies depending on the farming status of wild d. discoideum. when exposed to a toxic environment created by the use of ethidium bromide, it was shown that the number of sentinel cells per millimeter was lower for farmers than non-farmers. this was concluded by observing the trails left behind as the slugs migrated and counting the number of sentinel cells present in a millimeter. however, the number of sentinel cells does not affect the spore production and viability in farmers. farmers exposed to a toxic environment produce the same number of spores as farmers in a non-toxic environment, and the spore viability was the same between the farmers and non-farmers. when clade 2 burkholderia, or farmer-associated bacteria, are removed from the farmers, spore production and viability were similar to that of the non-farmers. thus, it is suggested that bacteria carried by the farmers provide an additional role of protection for the farmers against potential harm due to toxins or pathogens. classification and phylogeny in older classifications, dictyostelium was placed in the defunct polyphyletic class acrasiomycetes. this was a class of cellular slime molds, which was characterized by the aggregation of individual amoebae into a multicellular fruiting body, making it an important factor that related the acrasids to the dictyostelids. more recent genomic studies have shown that dictyostelium has maintained more of its ancestral genome diversity than plants and animals, although proteome-based phylogeny confirms that amoebozoa diverged from the animal–fungal lineage after the plant–animal split. subclass dictyosteliidae, order dictyosteliales is a monophyletic assemblage within the mycetozoa, a group that includes the protostelid, dictyostelid, and myxogastrid slime molds. elongation factor-1α (ef-1α) data analyses support mycetozoa as a monophyletic group, though rrna trees place it as a polyphyletic group. further, these data support the idea that the dictyostelid and myxogastrid are more closely related to each other than they are the protostelids. ef-1α analysis also placed the mycetozoa as the immediate outgroup for the animal-fungal clade. latest phylogenetic data place dictyostelids firmly within supergroup amoebozoa, along with myxomycetes. meanwhile, protostelids have turned out to be polyphyletic, their stalked fruiting bodies a convergent feature of multiple unrelated lineages. genome the d. discoideum genome sequencing project was completed and published in 2005 by an international collaboration of institutes. this was the first free-living protozoan genome to be fully sequenced. d. discoideum consists of a 34-mb haploid genome with a base composition of 77% and contains six chromosomes that encode around 12,500 proteins. sequencing of the d. discoideum genome provides a more intricate study of its cellular and developmental biology. tandem repeats of trinucleotides are very abundant in this genome; one class of the genome is clustered, leading researchers to believe it serves as centromeres. the repeats correspond to repeated sequences of amino acids and are thought to be expanded by nucleotide expansion. expansion of trinucleotide repeats also occurs in humans, in general leading to many diseases. learning how d. discoideum cells endure these amino acid repeats may provide insight to allow humans to tolerate them. every genome sequenced plays an important role in identifying genes that have been gained or lost over time. comparative genomic studies allow for comparison of eukaryotic genomes. a phylogeny based on the proteome showed that the amoebozoa deviated from the animal-fungal lineage after the plant-animal split. the d. discoideum genome is noteworthy because its many encoded proteins are commonly found in fungi, plants, and animals. databases dictybase - general genomic database about dictyostelium discoideum membranome database provides information about single-pass transmembrane proteins from dictyostelium and several other organisms