TikZ Mindmap: text in the nodes undesirably covered by connectors

Question

I created a mindmap (see below). I found my text was undesirably covered by the connectors. Is there a way to put the connector a layer below the text, or put the text a layer above the connector? I know I can bypass this problem by changing the node size, or the font size, or the sibling angle. But I prefer the current appearance so I don't want to change any of the parameters above. I just want to change the layers. Is there a way to do so?

\documentclass[12pt,twoside]{article}
\usepackage[english]{babel}
\usepackage[utf8]{inputenc}
\usepackage{tikz}
\usetikzlibrary{mindmap}

\pagestyle{empty}

\begin{document}

\begin{tikzpicture}[mindmap, grow cyclic, every node/.style=concept, concept color=green!80, 
  level 1/.append style={level distance=5cm, sibling angle=180},
  level 2/.append style={level distance=3cm, sibling angle=90}]


\node{Gram positive bacteria}
    child[concept color=orange!80]{ node{Firmicutes}    
        child{node{\textit{Listeria}}
        }
        child{node{\textit{Bacillus}}
        }
        child{node{\textit{Streptococcus}}
        }
        child{node{\textit{Enterococcus}}   
        }
    }   
    child[concept color=purple!30,]{ node{Actinobacteria}
        child{node{\textit{Streptomyces}}
        }
        child{node{\textit{Corynebacterium}}
        }
        child{node{\textit{Mycobacterium}}
        }
    }
;
\end{tikzpicture}

\end{document}

Answer 1

One cheap hack to bypass the problem described in your title is to manually hyphen text locally, where necessary. In your case, you could change lines 27 (for the sake of consistency), 30 and 32 of your code respectively to:

child[concept color=purple!30]{node{Actino\-bacteria}

...

child{node{\textit{Coryne\-bacterium}}

...

child{node{\textit{Myco\-bacterium}}

Answer 2

I used an extra node (mycobacterium) to write the text after the mindmap has been rendered.

\begin{tikzpicture}[mindmap, grow cyclic, every node/.style=concept, concept color=green!80, 
  level 1/.append style={level distance=5cm, sibling angle=180},
  level 2/.append style={level distance=3cm, sibling angle=90}]
  \node{Gram positive bacteria}
    child[concept color=orange!80]{ node{Firmicutes}    
        child{node{\textit{Listeria}}
        }
        child{node{\textit{Bacillus}}
        }
        child{node{\textit{Streptococcus}}
        }
        child{node{\textit{Enterococcus}}   
        }
    }   
    child[concept color=purple!30,]{ node{Actinobacteria}
        child{node{\textit{Streptomyces}}
        }
        child{node{\textit{Corynebacterium}}
        }
        child{node (mycobacterium) {}
        }
    };
  \node[extra concept,fill=none,draw=none] at (mycobacterium) {\textit{Mycobacterium}};
\end{tikzpicture}