## 1 Introduction  
Tuberculosis remains one of the top infectious killers worldwide [1]. Additionally, the continued emergence and spread of multidrug-resistant TB further demonstrates the urgent need for novel therapeutic approaches against _Mycobacterium tuberculosis_ (_Mtb_), the causative agent of tuberculosis (TB) in humans. The drug resistance of _Mtb_ is due in part to a well-armored cell wall, which is unique in composition and architecture. The outer membrane consists of an inner leaflet of very long chain mycolic acids covalently bound to an underlying arabinogalactan-peptidoglycan layer, and an outer leaflet composed of diverse nonoculently associated lipids such as trehalose 6,6'-dimyclate (TDM), phthito-cerol dimyccoerostate (PDIM), and sulfolipids [2, 3]. Because its structure is distinct from the outer membrane of Gram-negative bacteria, this outer layer is commonly referred to as the mycomembrane. Mycomembrane lipids are positioned to play important roles in intercellular interactions. Indeed, disruptions in lipid biosynthesis or trafficking attenuate pathogenesis, as has been reviewed elsewhere [4, 5, 6]. Perturbations in mycobacterial lipids are also correlated with defects in the formation of biofilms [7, 8, 9, 10, 11, 12, 13]. Broadly defined, biofilms are communities of microorganisms that are associated with a self-secreted extracellular matrix that is thought to serve structural and communication roles [14]. These communities can range from surface-attached colonies to pellicles at the air-liquid interface, with the latter being one of the most studied models for mycobacterial biofilms [15]. Importantly, several mycobacterial species have been shown to form biofilms in the clinical setting. The fast-growing non-tuberculous mycobacterium (NTM) _M. abscessus_ forms biofilms within the thickened alveolar walls and airways of cystic fibrosis patients [16], as well as in the lung cavity of a patient with chronic obstructive pulmonary disease [17]. [PERSON] et al. demonstrated a role for the biofilms of another NTM, _M. avium_, in bronchiolar and bronchial infections [18]. _Mtb_ was recently found to form biofilms in human lung samples with TB, and in this state _Mtb_ was protected from chemotherapeutic agents [19]. Moreover, mycobacteria species in this biofilm state have been found to be more resistant to antibiotics [20; 21]. Overall, the relevance of biofilms to clinical infections and treatment motivates investigating the genetic and molecular mechanisms by which they form. Diverse factors drive mycobacterial biofilm formation, as has been reviewed elsewhere [22; 23; 24] and in detail for multiple mycobacterial species by [PERSON] and [PERSON] [25]. For the two most highly studied species, _M. tuberculosis_ and _M. smegmatis_, the most consistent association has been with lipids, including free mycolic acids (FMA) [11; 13], mycolyl diacylglycerolides (MDAG) [26], monomeromycolyl diacylglycerolecar (MMDAG) [7; 27], mycolate wax esters (MWE) [7; 8; 27] and, in _M. smegmatis_, glycopidolipids (GPL) [9; 28]. Genetic alterations associated with changes in lipids can affect stages that are commonly defined for bacterial biofilms and are shared by mycobacteria: substratum attachment, intercellular aggregation, and architecture maturation. For example, in _M. smegmatis_, _lsr2_ disruption is required for intracellular aggregation, whereas _groE1I_ is required for maturation. Further, _groE1I_ has an unexpected role in stabilizing FAS II enzymes KasA/KasB, whose activity feeds into mycolic acid biosynthesis; the loss of _groE1I_ leads to the production of short chain mycolates (thought to be precursors to FMAs) [12]. The loss of _lsr2_ is suppressed by mutations in the GPL biosynthesis gene _mps_[29]. This contradicts studies showing that GPL is required for biofilm formation [9; 28], but suggests that this process depends on the integration and timing of diverse factors, and that any one factor, such as a single lipid class, cannot necessarily serve as a universal marker.